Originally Posted by

**Natasha1** A publisher has to choose a price £x for a new book. The total amount of money she will receive from sales is £y, where y = 20000x - 5000xsquared

a) find the price which gives the maximum amount of money from sales?

Is it f'(x) = 20000 - 10000x

So when the book cost £0 will she receive the maximum amount of money which is £20000.

**No, if you think in terms of the graph, it's clear**

This does not much sense? **exactly**

b) find the maximum amount of money from sales.

£20000