In a survey of employees at a fast food restaurant, it was determined that 13 cooked food, 16 washed dishes, 20 operated the cash register,
7 cooked food and washed dishes, 6 cooked food and operated the cash register, 8 washed dishes and operated the cash register, 3 did all
three jobs, and 5 did none of these jobs. Complete parts a) through f) below.

how many employees took the survey?