A two-day environmental clean up started at 9AM on the first day. The number of workers fluctuated as shown in the figure.

Suppose that the workers were paid 12 dollars per hour for work during the time period 9 am to 5 pm and were paid 18 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 = dollars

 
graph of number of workers vs. time; between t=0 hours and t=8 hours the graph behaves as a sine curve with centerline 35, amplitude 15 and period 16; between t=12 and t=20, the graph is constant at 20. Then, at t=20 the graph becomes a sine curve again, starting at its minimum and completing one period between t=20 and t=36. The graph is then constant at 20 until t=44, before increasing as a sine again until t=48.