Every morning Robert, a technician in the manufacturing plant, stops at Tool Supply to check out power impact drivers for use in assembly operations. At the start of every morning, Tool Supply has 30 power impact drivers available for checkout. Robert is always first in line and checks out 2 tools, even though he can only use one at a time. When queried about this by the manager, Robert states that, based on experience, 10% will have a failed or degraded battery. So, to increase his chances of having at least one power impact driver with a good (not failed or degraded) battery, he always checks out two.

a. What probability distribution should be used to determine the probability at least one power impact driver will have a good battery (not failed or degraded)?

b. What is the probability that Robert will have at least one power driver with a good battery?