An espresso stand has a single server. Customers arrive to the stand at the rate of $28$ per hour according to a Poison distribution. Service times are exponentially distributed with a service rate of $35$ customers per minute. If the arrival rate remains at $28$ customers per hour and the stand's manager wants to have the average time a customer spends in the system $($i$.$e$.,$ wait time line and service time$)$ to be a maximum of $6$ minutes on average, then the service rate must decrease by $2$ to $33$ customers per hour decrease by $3$ to $32$ customers per hour increase by $3$ to $38$ customers per hour increase by $2$ to $37$ customers per hour