The Manager of a Fast-Food Restaurant Determines That the Average $1.6321$

The manager of a fast-food restaurant determines that the average time that her customers wait for service is 2 minutes. Find the probability that a customer is served within the first 2 minutes.

A) $1.6321$
B) $0.6321$
C) $4.6321$
D) $3.6321$
E) $2.6321$