I was plotting 2 functions (the production function and the cost-of-production aka communication cost function) onto the same graph and looking only at the top-

I was plotting 2 functions (the production function and the cost-of-production aka communication cost function) onto the same graph and looking only at the top-right part where X > 0 and Y > 0, in this case, X = number of people and Y = money (either produced or consumed). The production function, because of its sqrt(N), looks like a U flipped on its side. Meanwhile, the cost function, because of its N^2, looks like a regular U. If you have a U sitting with its butt on 0,0, and a U lying down on 0,0, and you look only at the top-right coordinate plane, it'd look kind of like the letter gamma tilted 45 degrees. Regarding per-capita consumption and total consumption, if you have per-capita consumption, and you have N the total number of people, you can multiple per-capita consumption with the total number of people to get total consumption. If per-capita consumption varies with the number of people, then a bit of calculus is needed as you "integrate" per-capita consumption with respect to number of people to find "the area under the curve" which is your total consumption. But if the students have not yet learned calculus, I can see how it could be unfair to have them derive calculus during the test.