A student procrastinates, watching cars pass his house. After 10 black cars have passed, he will (finally) start his homework. He notices that the time between consecutive cars that pass is Exponentially distributed, and the times are independent, each with expected time of 1/5 of a minute. He also assumes that each car has a 30% chance of being black, and the colors of the cars are independent. How long should he expect to wait until the 10th black car arrives?