Zero marginal revenue

Statement

The total revenue is $R(q)=100q-2q^{2}$ (in €). Find the marginal revenue function and the quantity that makes it zero.

Solution

Marginal revenue is $MR(q)=R'(q)=100-4q$. $MR(q)=0\iff 100-4q=0\iff q=\boxed{25}.$