The rate at which a machine operator's efficiency, E (expressed as a percentage), changes with respect to time t is given by dE dt =30 - 10t, where t is the number of hours the, operator has been at work. bok a) Find E(t), given that the operator's efficiency after working 2 hr is 72%; that is, E(2) = 72. b) Use the answer in part (a) to find the operator's efficiency after 3 hr; after 5 hr. . . . a) E(t) = ce Lit b) The operator's efficiency after 3 hours is %. The operator's efficiency after 5 hours is urces %. ns n Too