the total revenue that a monopoly receives from selling different levels of output q is given by the function TR(q)=60q-4q^2 for q being equal to or greater than 0 and equal to or lesser than 15....

the total revenue that a monopoly receives from selling different levels of output q is given by the function TR(q)=60q-4q^2 for q being equal to or greater than 0 and equal to or lesser than 15. Explain why one cannot derive the inverse function q=f(TR)