I have combined function c(t)= 300t + 19000(0.995)^t. t represents how long (hours) a hose runs, while 19000(0.995)^t represents evaporation of a pool (by hour). The pools total capacity is 20500 gallons. How many hours will the hose have to run so that the pool is filled to it's maximum capacity? Preferably, I'd like to know how to solve it... My workbook says to use calculator though (TI-84) so can anyone tell me how to solve it with that at least? Moving the tracer thing doesn't work because I can't get it to be on 20500.