A circular conducting ring with radius $r_{0}=0.0420 \mathrm{~m}$ lies in the $x y-$ plane in a region of uniform magnetic field $\overrightarrow{\boldsymbol{B}}=B_{0}\left[1-3\left(t / t_{0}\right)^{2}+2\left(t / t_{0}\right)^{3}\right] \hat{\boldsymbol{k}} .$ In this expression, $t_{0}=0.0100 \mathrm{~s}$ and is constant, $t$ is time, $\hat{k}$ is the unit vector in the $+z$ -direction, and $B_{0}=0.0800 \mathrm{~T}$ and is constant. At points $a$ and $b$ (Fig. $\mathbf{P} 29.56$ ) there is a small gap in the ring with wires leading to an external circuit of resistance $R=12.0 \Omega .$ There is no