AMC 10B 2015 Problem 18

Johann has 64 fair coins. He flips all the coins. Any coin that lands on tails is tossed again. Coins that land on tails on the second toss are tossed a third time. What is the expected number of coins that are now heads?

Answer Choices
A. 32
B. 40
C. 48
D. 56
E. 64