Atelephone company in a town has 500 subscribers on its list and collects fixed changes of RS 300/-per subsriber per - Maths - Application of Derivatives

Question

Atelephone company in a town has 500 subscribers on its list and
collects fixed changes of RS 300/-per subsriber per year The
company proposes to increase the annual subscription and it is
believed that for every increase of Re 1/- on subscriber will
discontinue the service Find what increase will bring maximum
profit ?/

Gursheen kaur. · Accepted Answer

If the increase be Rs x per subscriber then
the rate will be 300 + x and subscribers left will be
500-x

therefore, acc to the given condition

If I be the new income, then

I = (300+x) (500-x)