HELP Need answer to this force due to charge problem

[matt85]

HELP! Need answer to this force due to charge problem!

Here it is:

Three charges are fixed in place as shown. The squares in the grid have sides of length s = 0.24 m. The magnitude of q is 3 mu or micro Coulombs (1 mu or micro Coulomb = 10-6 Coulombs), while the magnitude of Q is 4.5 mu or micro Coulombs. What is the magnitude of the net force on q due to the other two charges?

I really need the answer to the problem, it's killing me, I've worked on it for 2 hours and can't get it. The picture is attached.

Thanks a ton,
Matt

https://www.physicsforums.com/attachment.php?attachmentid=6103&stc=1&d=1137281964

 

[Astronuc]

How about writing the formula for electric force, and then putting in the numbers. Remember, the force and electric field are vector quantities, so one must use vector addition.