Billable hours per year style question

If I may I'd like to ask for help on the Excel 2007 formula to calculate billable hours per year.

The Data for the days worked per year is currently 245 as a pre calculated number

I've got the data for average hours worked per day it the top row and percentage of billable hours per year in the row immediately below it.

B30 is filled as by a formula 245 on a General Cell format

B31 is filled as 8.5 on a General Cell format

B32 is filled as 100 on a Percent format

I'm just a little stuck at =(B31*B32)*B30 being simple or using for future entry error checkings sake : =(B31*B32)*((B26*52)-(B27+B28+B29))