Cars Arrive at a Local JLUBE Franchise at the Rate

Multiple Choice

Cars arrive at a local JLUBE franchise at the rate of 1 every 12 minutes.Service times are exponentially distributed with an average of 15 minutes.Jack Burns,the JLUBE owner,has decided to open a second work bay,i.e. ,make the shop into a two-channel system.Under this new scheme,the total time an average customer spends in the system will be

A) 37 minutes.
B) 2.1 minutes.
C) 9.6 minutes.
D) 33.3 minutes.
E) 24.6 minutes.