1.7 Solve the below problem: (3) If Y1 is the total time between a customer's arrival in the store and departure from the service window and if Y2 is the time spent in line before reaching the window= the joint density of these variables is in: 053'2 c: Y1 500' fo1.y2)= {'3 , elsewhere. The random variable Y1 Y2 represents the time spent at the service window. Find E (Y1 Y2). [Hint Y1 has a gamma distribution with a = 2 and = 1= and Y2 has an exponential distribution with 16' = 1]