The Clean Pool company maintains residential swimming pools for customers in a city in Florida. Clean Pool has a regular maintenance schedule for all pools but also provides emergency service for customers requiring immediate help. For emergency repairs, Clean Pool has contract workers who are assigned 12 specific pools to be on call for. One such worker is Jaime who is assigned 12 specific pools in hisneighbourhood; in case of a call, he would have to repair them as soon as he could. It has been found that each of these pools require emergency repair approximately once every 40 days (assume Poisson arrivals) and that repair takes ½ of a day. Jaime finds this arrangement to be stress free, except when a customer calls with an emergency and Jaime can not help them immediately (i.e. he is working on another call at the time). How often does this happen (i.e., where a customer has to wait)?

a. less than or equal to 5% of the time

b. more than 5% of the time, but less than or equal to 10% of the time

c. more than 10% of the time, but less than or equal to 15% of the time

d. more than 15% of the time