10 motors are for sale in a warehouse. the motors sell for $100 each, but return you double your money for any defective that the purchaser may receive. find the expected net gain for the seller if the probability of any one motor being defective is 0.08.

my working:
expected net gain per motor = o.92 x 100 - 0.08 x200
expected net gain for 10motors = (o.92 x 100 - 0.08 x200) x 10 = 760

however the answers in my book stated that it was 840..