Three point$-$like charges are placed at the corners of a rectangle as shown in the figure, $a=36\mathrm{.}0cm$ and $b=66\mathrm{.}0cm.$

Find the magnitude of the electric force exerted on the charge $q_1.$ Let $q_1=-1\mathrm{.}20C,q_2=+2\mathrm{.}70C,q_3=+4\mathrm{.}50C.$