please help

Quiz 4.6 (A) Two computers use modems and a telephone line to transfer e-mait' and Internet news every hour. At the start of a data call, the modems at each end of the line negotiate a speed that depends on the line quality. When the negotiated speed is tow, the computers reduce the amount of news that they transfer. The number of bits transmitted L and the speed 8 in bits per second have the joint PMF PL.3(i,b) b=l4,400 b=21,600 b=28,800 I = 513, 400 0.2 0.1 0.05 1 = 2, 592, 000 0.05 0.1 0.2 (4'57) I = 7, 776, 000 0 0.1 0.2 Let T denote the number of seconds needed for the transfer: Express T as a function of L and B. What is the PMF of T ? (3) Find the CDF and the PDF of W = X Y when random variables X and Y have joint PDF 105x51,05y51. 0 otherwise. (4'58) fx.r (x, y) = {