13) You are setting the combination on a three-digit lock. You want to use the numbers 381 but don't care what order they are in? Is this premutation or combination, what are the possibilities?

The tuition costs, c, for a local community college are modeled by c(h) = 250 + 200h, where h represents the number of credit hours taken. the local state university has tuition costs, s, modeled by the function s(h) = 300 + 180h. how many credit hours will a student have to take for the two tuition costs to be equal? round the answer to the nearest tenth of an hour.