Consider the random variables X and Y that represent the number of vehicles that arrive at 2 separate street corners during a certain 2-tninute period. These street corners arc fairly close together so it is important that traffic engineers deal with them jointly if necessary. The joint distribution of X and Y is known to be for x = 0 , 1 , 2 , . . . , and y = 0 , 1 , 2 , . . ..
(a) Are the two random variables X and Y independent? Explain why or why not.
(b) What is the probability that during the time period in question less than 4 vehicles arrive at the two street corners?