Since the shipment can be rejected if "at least one" is defective, we have to use the common short cut:
P(at least 1) = P(all) - P(none)
= 1 - P(5 GOOD toys selected in 5 picks)
= 1 - 0.9*0.9*0.9*0.9*0.9
= 1 - 0.9^5
The answer choice should reflect an exponent.
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