In a local hospital, a nurse administrator needs to know how many times per shift a nurse is called for on average by the patients on the floor, in order to determine how much staff is needed per shift. Through tracking the number of times the nurse bell is rung for 100 patients, the following data was collected: 10 patients rang the bell 0 times, 20 patients rang the bell 1 time, 25 patients rang the bell 2 times, 15 patients rang the bell 3 times, 20 patients rang the bell 4 times, and 10 patients rang the bell 5 times. What is the expected value for the average number of times that the bell is rung? Show your PDF and your EV equation.