A straight conducting rod $PQ$ is executing SHM in $xy$-plane from $x=-d$ to $x=+d$. Its mean position is $x=0$ and its length is along $y$-axis. There exists a uniform magnetic field $B$ from $x=-d$ to $x=0$ pointing inward normal to the paper and from $x=0$ to $x=+d$ there exists another uniform magnetic field of same magnitude $B$ but pointing outward normal to the plane of the paper. At the instant $t=0$, the rod is at $x=0$ and moving to the right. The induced emf $\left(\epsilon \right)$ across the rod $PQ$ vs time $\left(t\right)$ graph will be