For questions $13$ to $17$: Consider the following system: Customers arrive to a bank with two tellers. Customers have an exponential inter$-$arrival time of $15$ minutes and exponential service time of $10$ minutes.

Management needs to fire one of the tellers and keep the system only with one teller. If they implement this change in the bank, how many customers $($on average$)$ would be waiting in line?

Group of answer choices

$0\mathrm{.}66$

$1\mathrm{.}33$

$2\mathrm{.}00$

$3\mathrm{.}33$

None of the other answers