Combining an IF function with a WORKDAY function

So if E4="P7" do you want to add 10 workdays to the date.....or just add 10 days and then move to next workday if a weekend results?

For the former...

=WORKDAY(D4,IF(E4="P7",10,IF(E4="P6",15,IF(E4="P5",20,IF(E4="P4",25)))))

or the latter

=WORKDAY(D4+IF(E4="P7",10,IF(E4="P6",15,IF(E4="P5",20,IF(E4="P4",25))))-1,1)