Residual income question in practice exam

Hi

In the F2 practice exam on this website there is a question on residual income which I cannot get the correct answer to using the calculation I believe is correct.. the question is ‘an investment division currently has net assets of $500,000 and is earning profits of $70,000 per annum. The divisional manager is considering a new investment which will cost $20,000 and will generate additional profits of $2,200 per annum. The company has a cost of finance of 10%. What is the RI for the division with and without the new investment?’
Using the calculation per the study books I would do for
without investment – 70,000 – (500,000*10%)= 20,000
and for the new investment 72,200 – (520,000*10%) = 20,200.

However the answer in the exam says it is 30,000 and 29,800 respectively.

Please help!