Help in Formula using 'if'

Query.jpg

Image Location: -
http://s9.postimg.org/a6q2hmdv3/Query.jpg

Here i want to put a Formula in 'G' column field where 7100 appears.

At the moment i am myself calculating 1100 + 1000 + 5000 and adding and writing 7100 in the G column. I want a Formula where Numbers in column 'E' are only added if column 'D' has something written in front of it for e.g: - 10 or 11, or 12, 555 , 666 & so on...... If nothing is written in column 'D' like for e.g:- next to 4000 then this 4000 should not be added to 7100 and likewise the last 'E' field 1000 also will not be added as nothing in written in column 'D' against it.

Requesting for help in coming up with such a formula.
Note- This Image is for representation. Column 'D', 'E' has around 100 rows