KM has a call center that receives an average of 200 calls per hour (time between calls are exponentially distrusted). It takes an operator an average of 2.75 minutes to handle a call. If a caller gets a busy signal, the call center assumes that he/she will call another company, and KM will lose and average of $9 in profit. The cost of keeping a phone line open is $4 per hour. How many operations should KM have on duty?