A two-day environmental clean up started at 9AM on the first day. The number of workers fluctuated as shown in the following figure. 18 48 Suppose that the workers were paid 15 dollars per hour for work during the time period 9 am to 5 pm and were paid 22.5 dollars per hour for work during the rest of the day. What would the total personnel costs of the clean up have been under these conditions? total cost = 480 dollars