The Length of Time (In Months)that a Cashier Works for a Certain

Essay

The length of time (in months)that a cashier works for a certain fast food restaurant is
exponentially distributed with a mean of 7 months.
a. Find the probability that a cashier works for the restaurant for at least 2 years.
b. Find the probability that a cashier works for the restaurant for less than 1 month.