Aletter that represents an unknown number

Mr switzer needs to buy new 1-foot tiles to cover his bathroom floor. the floor is 12 feet long and 8 feet wide. each square foot of tile will cost $1.79. in dollars what will be the total cost of the tiles he needs to buy.

Which of the following would be a good name for the function that takes the weight of a box and returns the energy needed to lift it?

Which one is the correct answer, and why?