What could represent the total cost

d

Step-by-step explanation:

vertical axis = total cost, horizontal axis = number of cd

it would start higher on the vertical axis as the starting cost is higher (7000 vs 5000), but the line would be less steep as the increase in cost between cds is less.

18

step-by-step explanation:

draw the shape and you will see that f and k are actually at adjacent vertices (points of the hexagon that are neighboring).   so find the distance between (1,2) and (4,2).   that is easy since (1,2) and (4,2) is just a vertical distance to count, which is 3.   it is a regular polygon which means all sides are congruent.   you have 6 sides (hexa) so multiply 6 by 3 to receive 18.