Suppose that the amount of time one spends in a bank is exponentially distributed with a mean of 10 minutes. what is the probability that a customer will spend more than 15 minutes total in the bank g

Suppose that the amount of time one spends in a bank is exponentially distributed with a mean of 10 minutes. what is the probability that a customer will spend more than 15 minutes total in the bank given that the customer is still in the bank after 10 minutes?