Total of two different field values combine to report as one sum.

I have an access table that lists a vary of different departments (13) as field. and a field titled hours that contains numbers. I am attempting to combine departments to find a sum total of both under a new name. something like;

dept. hours
office  10
whse   30
prod    20
shipp    15
 and would like
process  30 (office+whse)
inventory 45 (whse+Shipp)

in either, a query or report but ultimately a report.