I tried solve that problem and for me the maximum income is $3000$ because $1000\times 3$.
But the answer is $3600$! Can anybody explain me how it works? Thanks
James has $\$1000$ and wants to invest it in a project. He knows that each dollar brings $\$2$ income per month. He may rent a number of billboards for $\$100$ each. Each billboard increases one dollar’s income by $\$1$ per month. Find the James’ maximal total month income. Write your answer in dollars.