YourNurse (YN) Inc. uses certified nurses to answer medical queries from customers over the phone. When patients call into YN, they are first asked to provide their zip code, which then allows YN to route their call to the call center nearest to the patient (it operates 10 across the country). Which single suggestion in the following list (and explanation) is most likely to reduce the average time callers wait before speaking with a nurse? 

a. Run an advertising campaign to increase demand and to better utilize its nurses. 

b. Train its nurses so that they spend more time answering the patients’ questions. 

c. Instead of using callers’ zip codes, route calls to the call center with the fewest callers to help prevent situations in which there are idle nurses at the same time that there are callers on hold. 

d. Play a recording of useful medical information while callers are on hold so as to decrease their perception of how long they are waiting. e. None of the above.