answer on cfai mock contradicts text purposes, valuation, afternoon

chunty

Question 51 in the afternoon session essentially asks us to calculate FCFE from EBITDA.

In the answer key, their answer shows WCinv being calculated as the change in working capital:
[(CAt - CLt) - (CAt-1 - CLt-1)]

However, in the text on pg. 391 v.4, bottom of the page it says:

"Although working capital is often defined as current assets minus current liabilities, working capital for cash flow and valuation purposes is defined to exclude cash and short-term debt... ...when finding the net increase in working capital for the purpose of calculating free cash flow, we define working capital to exclude [continues on pg. 392] cash and cash equivalents as well as notes payable and the current portion of long-term debt."

Any ideas?