A charge of 22.5$\mu \mathrm{C}$ is located at $(4.40 \mathrm{m}, 6.22 \mathrm{m}),$ and a charge of $-14.2 \mu \mathrm{C}$ is located at $(-4.50 \mathrm{m}, 6.75 \mathrm{m}) .$ What charge must be located at $(2.23 \mathrm{m},-3.31 \mathrm{m})$ if the electric potential is to be zero at the origin?