Find a Doctor is a small startup that helps people find a physician who best meets their needs (location, insurance accepted, etc.). During a “slow” time for it, it has seven staff members taking calls from customers. On average, one call arrives every six minutes (with a standard deviation of six). Each staff member spends 20 minutes with each customer (on average, with a standard deviation of 30). What is the probability that one of its staff members is busy (as a percent)?