In a skateboard factory, marginal cost decreases as more are made. Marginal cost for making x skateboards a month, dollars per board, is C'(x)=20/(√(1+0.04x)). Given that fixed costs are 2000, how much would it cost to make 200 boards in a month? I thought the answer was 5000 but I am wrong and now a bit confused as to why and what it actually would be.