A worker new to a job will improve his efficiency with time so that it takes him fewer hours to produce an item with each day on the job, up to a certain point. Suppose the rate of change of the number of hours it takes a worker in a certain factory to produce the xth item is given by H′(x) = 20 - 2x.
(a) What is the total number of hours required to produce the first 5 items?
(b) What is the total number of hours required to produce the first 10 items?