Two charges $q=+4\mathrm{.}7C$ are fixed a distance $d=7\mathrm{.}0cm$ apart $($see the figure$).($a$)$ With $V=0$ at infinity, what is the electric potential at

point C$?($b$)$ You bring a third charge $q=+4\mathrm{.}7$ C from infinity to $C.$ How much work must you do$?($c$)$ What is the potential energy $U$ of

the three$-$charge configuration when the third charge is in place?