How do I find the net force of the particles?

Three particles are placed in a line. The left particle has a charge of 鈭?7 碌C, the middle, qm = +45 碌C, and the right, qr = 鈭?0 碌C. The middle particle is 72 cm from each of the others.

(a) Find the net force on the middle particle.

Magnitude

____N



(b) Find the net force on the right particle.

Magnitude

____





Can some one teach me how to do this problem? All help is appreciated. Thank you!How do I find the net force of the particles?
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