text: who knows how to write a cost function (linear)? fixed cost, 220$; 5 items cost $4610 to produce  a cab co charges a base rate of $2.00 plus 20 cents per minute. let c(x) be the cost in dollars  i wrote c(x) =1756x = 220 for the first problem and  c(x) = 2.00x - 0.20 for the second fixed cost becomes the intercept of your equation. slope is given by the cost per item. you can calculate the cost per item, as (4610-220)/5 (=total cost - fixed cost, the result divided by number of items). this gives a slope of 4390/5=878  so, c(x)= 220 + 878x x stands for items, result for c(x) is in dollars  (notice that you are assumingo you can produce items one by one and not at packs of five; otherwise you wouldn't have a straight line because to produce one or to produce five would have the same cost) ---- in the second case, base rate 2.00 is the intercept and cents per minute is the slope; x stands for minutes, result for c(x) is in dollars: c(x) = 2.00 + 0.20x try and figure how a cab co charge works...