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.
This does not much sense?
b) find the maximum amount of money from sales.