A magnetic field, directed along z axis, varies as B = B0 x/a. where a is a positive constant. A square loop (of side l ), made of copper, is placed with its edges parallel to the x and y axes. If the loop is made to move with a constant velocity V0 , directed along x axis; the emf induced in it, would be
(1) B0 V0 \(\frac{l^2}{a}\)
(2) B0 V0 l
(3) B0 V0 \(\frac{l^2}{2a}\)
(4) B0 V0 \(\frac{l^3}{a^2}\)