Why does profit maximisation occur where MR=MC?

When MR>MCThe change in total revenue as a result of increasing output by one additional unit is greater than the change in total costs.Profit can still be made so firms increase output until MR = MC and they cannot benefit from more profit by increasing output further.When MR<MCThe change in total revenue as a result of increasing output by one is less than the change in total costs. This means the firm is losing profit thus making it unprofitable to do so.Profit is being lost so firms decrease output by one unit until MR = MC is met.