What is the formula for the following arithmetic sequence? 12, 6, 0, -6, ...

a. an = 12 + (-6)( n - 1)
b. an = -6 + 12( n - 1)
c. an = 6 + 12( n - 1)
d. an = 12 + 6( n - 1)

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.