The cost C of printing a magazine is jointly proportional to the number of pages p in the magazine and the number of magazines printed m. (Use k for the constant of proportionality.)
(a) Write an equation that expresses this joint variation.
(b) Find the constant of proportionality if the printing cost is $65,550 for 3800 copies of a 115-page magazine.
(c) How much would the printing cost be for 3500 copies of a 84-page magazine?