Finding Expected Value for a Magazine Sweepstakes Reader’s Digest recently ran a sweepstakes in which prizes were listed along with the chances of winning:

$1,000,000 (1 chance in 90,000,000), $100,000 (1 chance in 110,000,000), $25,000 (1 chance in 110,000,000), $5000 (1 chance in 36,667,000), and $2500 (1 chance in 27,500,000).

a. Find the expected value of the amount won for one entry.

b. Find the expected value if the cost of entering this sweepstakes is the cost of a postage stamp. Is it worth entering this contest?