trading loss

Hello Tutor, there is another question shown as follows:
Trancis is a sole trader who has been in business for many years preparing accounts to 5 April each year. His recent results have been as follows:
y/e 5 April 2014 Profit ……………………16000
y/e 5 April 2015 Loss……………………..(25000)
Francis has gross invetment income of £3000 each year. He is expected to make trading profits of around £12,000 per annum over the next few years.
What is the trading loss to carry forward to the tax year 2015/2016 if Francis makes the most advantageous claim for loss relief?
the answer is 6000, would you please help me?
many thanks