I need help with the following questions please.

dE The rate at which a machine operator's efficiency, E (expressed as a percentage), changes with respect to time t is given by - =35 -12t, where t is the number of hours the operator has been at work. a) Find E(t), given that the operator's efficiency after working 2 hr is 79%; that is, E(2) = 79. b) Use the answer in part (a) to find the operator's efficiency after 3 hr; after 5 hr. a) E(t) = b) The operator's efficiency after 3 hours is %. The operator's efficiency after 5 hours is %.Approximate the area under the graph of F(x) = 0.6x3 + 6x2 - 0.6x - 6 over the interval [- T, - 2] using 5 subintervals. Use the left endpoints to nd the heights of the rectangles. The area is approximately square units. (Type an integer or a decimal.)