Abox contains 16 transistors, 4 of which are defective. if 4 are selected at random, find the probability that a. all are defective. b. none are defective.

The u-drive rent-a-truck company plans to spend $13 million on 320 new vehicles. each commercial van will cost $25 comma 000, each small truck $50 comma 000, and each large truck  $80 comma 000. past experience shows that they need twice as many vans as small trucks. how many of each type of vehicle can they buy?