hello everyone today my calc class went over optimization but i still do not fully understand it. i've been trying to do the following problem:

the main problem im having is that i don't know where to start and what exactly am i finding. any pointers on how to tackle questions like is much appreciated.A farmer wants to fence an area of 13.5 million square feet in a rectangular field and then divide it in half with a fence parallel to one of the sides of the rectangle. How can he do this so as to minimize the cost of the fence? (Give the dimensions in increasing order.)