A conceptual smartphone design uses a parachute technique to avoid severe damage to the screen and phone-case. Each of four nozzles located on the case might be either functional or defective after a year. The probability that a year-old nozzle is functional is 0.20 and assume that the nozzles fail independently. If at least two nozzles are functional, the phone will not be damaged in a drop. Otherwise, it will necessarily be damaged in a drop.
a) Describe the sample space in terms of the condition (functional or defective) of each nozzle after a year. Let "F" denote a functional nozzle after a year and "D" denote a defective one.
b) How many outcomes are in the event defined by exactly two defective nozzles?