A roulette wheel has 38 slots in which the ball can land. Two of the slots are green, 18 are red, and 18 are black. The ball is equally likely to land in any slot. The roulette wheel is going to be spun twice, and the outcomes of the two spins are independent. The probability that the ball lands on black the first time and on the green the second time is:
a. 0.2136
b. 0.2244
c. 0.2500
d. 0.5000