Residual income after investment

On the page 74, BPP practice and revision Kit F5 has the following question:
Box Co 20 mins
The following scenario relates to questions 275 – 279.
Box Co has an operating profit of $20,000, and operating assets of $95,000. The cost of capital is 12%. There is a proposed investment of $10,000 which will increase the operating profit by $1,400.

276.What is the RI with and without the proposed investment?
Without investment: ? $
With investment: ? $

The answer in the book is as follow:

276 The correct answers are: Before investment: $8,600, After investment $7,950.

Before Investment After Investment
$ $
Divisional profit 20,000 21,400
Depreciation (850)
Imputed interest (12% of $95,000) (11,400)
Imputed interest (12% of $105,000) (12,600)
Residual income 8,600 7,950
I think that the information given in the question is not adequate. There is no information about the depreciation after investment. I wonder how can derive the depreciation of $850 to arrive at the residual income of 7,950 after investment. If there is no depreciation, the answer should be 8800 for residual income after investment!
Maybe it is a typo of this book!
Please help me to explain this!
Thank you!