Figure $($a$)$ shows two wires, each carrying a current. Wire $1$ consists of a circular arc of radius R$=0\mathrm{.}024$m and two radial lengths; it carries current i$\_(1)=2\mathrm{.}2$A in the direction indicated. Wire $2$ is long and straight; it carries a current i$\_(2)$ that can be varied; and it is at distance $($R$)/(2)$ from the center of the arc. The net magnetic field vec$($B$)$ due to the two currents is measured at the center of curvature of the arc. Figure $($b$)$ is a plot of the component of vec$($B$)$ in the direction perpendicular to the figure as a function of current i$\_(2).$ The horizontal scale is set by i$\_(2$s$)=1\mathrm{.}0$A$.$ What is the angle subtended by the arc? $($a$)($b$)$