Calculus 1 please.

I'm building a 300 ft2 rectangular deck outside of my house, and I want to fence it in. I don't need fencing on the side where my house is, so I only need fencing on three sides (see the picture). The fencing opposite my house costs 3 dollars/ft while the fencing on the other two sides costs 2 dollars/ft. The fence length opposite my house cannot be less than 10 ft and not more than 30 ft. 2 dollars/ft fencing DECK 2 dollars/ft fencing 3 dollars/ft fencing What would be the least possible cost of the fencing