A square-shaped conducting wire loop of dimension a moving parallel...

A square-shaped conducting wire loop of dimension $a$ moving parallel to the $\mathrm{x}$-axis approaches a square region of size $b(a < b)$ where a uniform magnetic field B exists pointing into the plane of the paper (see figure). As the loop passes through this region, the plot correctly depicting its speed $(v)$ as a function of $x$ is