How would I find a cost function if only given the fixed cost and variable cost?

A company makes two grades of paint, grade I, guaranteed for 5 years, and grade II, guaranteed for 10 years. A gallon of grade I costs $3.10 to make, while a gallon of grade Il costs $3.60 to make. The weekly fixed costs are $3950. Step 1 of 2: Find the cost function C(x, y) for making x gallons of grade I and y gallons of grade II.

Your college newspaper, The Collegiate Investigator, has fixed production costs of $72 per edition and marginal printing and distribution costs of 39¢ per copy. The Collegiate Investigator sells for 49¢ per copy. (a) Write down the associated cost function C(x) in dollars. C(x) =        Write down the revenue function R(x) in dollars. R(x) =        Write down the profit function P(x) in dollars. P(x) =        (b) What profit (or loss) results from the sale of 500 copies of The Collegiate Investigator? $  (c) How many copies should be sold in order to break even?  copies