Answer:a)$195,500 b) $10,735 c)$6,900
Explanation
a)adjusted basis of Kevin’s Bluebird stock on December 31, 2020?
1,000 shares was bought for $115,000
Therefore it was bought at  $115 per share
Also 
750 shares was bought at  $80,500 and therefore bought at 107.33 per share 
So in total of 1750 shares, He  spent $195,500    ($115,000+ $80,500)
b.On December 12, 2020,he bought  shares at 107.33 per share  
500 shares would be  500 x $107.33=$53, 665    
Therefore,   Kevin’s recognized gain or loss from the’ sale of Bluebird stock on March 1, 2021 would be 
 $64,400- $53, 665 = $10,735
c.Assuming he cannot identify the shares sold, then we can say they are sold on a FIFO ( first in first out) basis. So we would consider the shares bought on October 3, 2020
so we have that
500 x $115=$57,500
$64,400 - $57,500 = $6,900