You can rent time on computers at the local copy center for an $8 setup charge and an additional $4.50 for every 10 minutes. How much time can be rented for $21?

Select the choice below and fill in the answer box to complete choice.

A) The independent variable is rental cost (r), in dollars, and the dependent variable is time(t) in minutes. The linear function that models this situation is t=

B) The independent variable is time(t), in minutes, and the dependent variable is rental cost(r), in dollars. The linear function that models this situation is r=

( simplify the answer)

--- minutes can be rented for $21.

A linear model (is or is not) reasonable for this situation?