Calculate cost per week for project

I need some help with financial in excel 2003. I try to calculate my cost per week for my project .. I have 50 resources to calculate cost week per week

on column A1 I have rate per hours
on column B1 I have total cost per year
on column C1 I have the total hours per week the ressource his working. I calculate in FTE's = 1FTE = 40 hours

How can I do the sum per week - every week without having to do =sum(A1*B1*C1) for 50 persons

See excel spreadsheet for a better picture related to my question.