A$21-$loop circular coil $19$ cmcm in diameter lies in the xyxy plane. The current in each loop of the coil is $7\mathrm{.}8$AA clockwise, and an external magnetic field B$=(0\mathrm{.}6$i$^+0\mathrm{.}9$j$^0\mathrm{.}6$k$^)$TB$=(0\mathrm{.}6$i$^+0\mathrm{.}9$j$^0\mathrm{.}6$k$^)$T passes through the coil. Determine the potential energy UU of the coil in the field $($take UU $=0$ at $=$ $/2$$/2).$

Express your answer in Joules.