Question

A contractor is to build a warehouse who's rectangular floor will have an area of 4000 square feet. The warehouse will be separated into two rectangular rooms by and interior wall. The cost of the exterior wall is $175 per linear foot and the cost of the interior wall is $125 per linear foot. And the cost of the interior wall is $125 per linear foot. Express the contractors cost for building the walls, C, as a function of one of the dimensions of the warehouse's rectangular floor, x.

Answer 1

I'm having trouble approaching this. I found the first equation which is
Y=4000-x but I don't know what to do next.

Answer 2

Sorry I meant y=4000/x

Answer 3

hint: