so you would essentially plug in 475 into t, then plug into a handy TI-84 Plus calculator. but since it has to be explained, long way it is. 400+0.05(475-80) subtract 475 from 80 to get 400+0.05(395). now you will multiply 0.05 and 395 to get 400+19.75. now you have a simple addition so the answer is 419.75. wait theres no error ahhhh. hold on