A running track is 1 mile long. Two runners start on it at the same time. The speed of Runner i is Xi, i = 1 and 2. Suppose Xi ~ exp(λi), i = 1, 2, and X1 and X2 are independent. The mean speed of Runner 1 is 20 mph and that of Runner 2 is 22 mph. What is the probability that Runner 1 wins the race?