The time it takes for a customer to transact business at the window of the US Post Office branch in Sweet Briar, Texas, is exponentially distributed with a mean of 5.0 minutes. Four customers have just been processed in the last two minutes. How likely is it that the next customer will take
a. More than 5 minutes to process?
b. Less than 1 minute?
c. Between 3 and 4 minutes?