求助bpp f9书有错？

bpp f9 text book p119:

work-in-prgress period=(average wip*degree of wip completion * 365days)/ cost of sales是否有错？因为我在revision book 第六题中为, work in progress period=(wip * 365)/ (cost of sales * degree of completion), 自我感觉后者对,请教哪个是正确的.谢谢!