Take q1=25uC at (0,1), q2=20uC. at (2,0), and q3=? at (2,2). IF the force on q1 points in the -x direction, (a) what is q3 and (b) what is the magnitude of the force on q1? F=k(q1,q2)/r^2 coulombs law I know since q1 points in the -x direction that q3=q2. So (a)=20uC. I'm not sure how to go about part b.