How do I determine cost basis for RSU/ESPP during cash/stock exchange acquisition?

I have vested RSU/ESPP SanDisk stocks, and then acquired by Western Digital in 2016 with $67.5 in cash and remaining exchange of 0.2387 shares of WDC stocks at $36.74. How do I determine the cost basis for these WDC stocks when sold?  Is it $36.74 per share?  Is there a difference between RSU or ESPP?