A particularly long traffic light at the intersection is green 20% of the time. A car approaches this intersection once each and every day. Let X represents the number of days the car faces a green light. Suppose that each day represents independent trial:
a) Find out the probability that the light is green on exactly three days over a ten day period.
b) Find out the probability that the light is green on at least three days over a ten day period.
c) Find out the expected value of the number of days the car encounters a green light over a ten day period.
d) Find out the standard deviation of the number of days the car encounters a green light over a ten day period.