Four loads are placed in the plan at the following positions: r$1=4\mathrm{.}00$ cm i $,$ r$2=-3\mathrm{.}50$ cm j$,$ r$3=(-1\mathrm{.}50$i$+1\mathrm{.}90$j$)$ cm and r$4=(0\mathrm{.}40$i $+0\mathrm{.}50$j$)$ em$.$ The load values are q$1=2\mathrm{.}00$C$,$ q$2=-1\mathrm{.}80$C q$3=-2\mathrm{.}40$C and q$4=1\mathrm{.}10$C$.$ Calculate the force exerted on load q$1.$

a$.$ Express your answer in terms of unit vectors.

b$.$ Express your answer in terms of modulus and orientation.