Trading Profit Assessment BPP kit qs 101

Stefan started trading on 1 January 2019. His profits for the first six months of trading to 30 June 2019 were
£3,000 each month. Stefan estimates that his profits will be £4,000 each month for the next six months of trading
to 31 December 2019 and then £5,000 each month thereafter for the foreseeable future.

Compute Stefan’s trading income for the tax years 2018/19, 2019/20 and
2020/21 if he chooses 30 April as his accounting date.

Sir wouldnt it be 9000 for 18/19 ,42000 for 19/20(first 12 months-3000*6+4000*6) and 60000(5000*12)?
but the answer is 9000,45333,50000.??