Barber College Is the Best Deal in Town! for Only

Multiple Choice

Barber College is the best deal in town! For only $5,you can get a shampoo and cut by any one of four untrained stylists completed in 7.5 minutes on average.Perhaps this is why customers show up on average two minutes apart (both interarrival times and service times are exponentially distributed) .
-What percentage of the time are the four stylists working with customers?

A) 94%
B) 90%
C) 84%
D) 80%