Disregard blank (no value)

I cant seem to find reference to what I think are the more simple instructions, so apologies for asking "Dummy" questions.

I have a simple 2 cell addition in E6 =SUM(E5:F5)
This is duplicated for many rows.

I need to amend this to disregard if there is no value in F5 (blank)
is this possible?

Cheers Dave, perfect

If I now wanted to CAP the total to say 150, as the maximum allowed, is there an easy way to do that?

I'm saying even if the total was 156 or even 212 then the cell would read 150?

Thanks for your help