W(t) 2 3cos[ 4 1 4 2 The water level of a certain body of water is changing at a rate of , inches per hour, where t represents hours since 12 am. Part A: Using correct units, explain the meaning of "Dwmdf in terms of the context of this problem. (1 point) Part B: Write the integral that represents the number of inches that the water level changes from 7 pm. to midnight. (2 points) Part C: Use your calculator to evaluate your integral from Part B. Explain the meaning of the answer in terms of the context. (3 points) Part D: What is the average hourly number of inches that the water level changes for this lake in one day? (4 points)