(4)   Stock-Based Compensation

Liberty grants, to certain of its directors, employees and employees of its subsidiaries, restricted stock, restricted stock units (“RSUs”) and stock options to purchase shares of its common stock (collectively, "Awards"). The Company measures the cost of employee services received in exchange for an equity classified Award (such as stock options and restricted stock) based on the grant-date fair value (“GDFV”) of the Award, and recognizes that cost over the period during which the employee is required to provide service (usually the vesting period of the Award). The Company measures the cost of employee services received in exchange for a liability classified Award based on the current fair value of the Award, and remeasures the fair value of the Award at each reporting date.

Included in the accompanying condensed consolidated statements of operations are the following amounts of stock-based compensation, as discussed below:

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Liberty—Grants of Awards

Awards granted during the six months ended June 30, 2020 are summarized as follows:

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The Company did not grant any options to purchase Series A or Series B Liberty SiriusXM, Liberty Braves or Liberty Formula One common stock during the six months ended June 30, 2020.

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Also during the six months ended June 30, 2020, the Company granted 9 thousand, 3 thousand and 7 thousand time-based RSUs of Series C common stock of Liberty SiriusXM, Liberty Braves and Liberty Formula One, respectively, to our CEO. The RSUs had a GDFV of $33.11, $18.17 and $24.68 per share, respectively, and cliff vest on December 10, 2020. These RSU grants were issued in lieu of our CEO receiving 50% of his remaining base salary for the last three quarters of calendar year 2020, and he has waived his right to receive the other 50%, in each case, in light of the ongoing financial impact of COVID-19.

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Liberty calculates the GDFV for all of its equity classified Awards and the subsequent remeasurement of its liability classified Awards using the Black-Scholes Model. Liberty estimates the expected term of the Awards based on historical exercise and forfeiture data. The volatility used in the calculation for Awards is based on the historical volatility of Liberty common stock and the implied volatility of publicly traded Liberty options. Liberty uses a zero dividend rate and the risk-free rate for Treasury Bonds with a term similar to that of the subject Awards.

Liberty—Outstanding Awards

The following tables present the number and weighted average exercise price ("WAEP") of Awards to purchase Liberty common stock granted to certain officers, employees and directors of the Company, as well as the weighted average remaining life and aggregate intrinsic value of the Awards.  

Liberty SiriusXM

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Liberty Braves

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Liberty Formula One

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As of June 30, 2020, the total unrecognized compensation cost related to unvested Awards was approximately $35 million. Such amount will be recognized in the Company's condensed consolidated statements of operations over a weighted average period of approximately 2.1 years.

As of June 30, 2020, Liberty reserved 10.1 million, 1.4 million and 10.0 million shares of Series A and Series C common stock of Liberty SiriusXM, Liberty Braves and Liberty Formula One, respectively, for issuance under exercise privileges of outstanding stock Awards.

Sirius XM Holdings — Stock-based Compensation

Sirius XM Holdings granted various types of stock awards to its employees during the six months ended June 30, 2020. As of June 30, 2020, Sirius XM Holdings has approximately 201 million options outstanding of which approximately 143 million are exercisable, each with a WAEP per share of $4.58 and $4.07, respectively. The aggregate intrinsic value of Sirius XM Holdings options outstanding and exercisable as of June 30, 2020 is $294 million and $265 million, respectively. During the six months ended June 30, 2020, Sirius XM Holdings granted approximately 7 million nonvested

RSUs with a GDFV per share of $7.01. The stock-based compensation expense related to Sirius XM Holdings was $52 million and $57 million for the three months ended June 30, 2020 and 2019, respectively, and $107 million and $106 million for the six months ended June 30, 2020 and 2019, respectively. In addition, the acquisition and restructuring costs recognized by Sirius XM Holdings during the six months ended June 30, 2019 includes $21 million of stock-based compensation. As of June 30, 2020, the total unrecognized compensation cost related to unvested Sirius XM Holdings stock options and RSUs was $342 million. The Sirius XM Holdings unrecognized compensation cost will be recognized in the Company's condensed consolidated statements of operations over a weighted average period of approximately 2.2 years.