A negatively and uniformly charged disk is rotating in a clockwise direction as viewed from above. The direction of magnetic field at a point A is

Question

 

$\begin {array} {1 1} (a)\;Into\: the\: plane & \quad (b)\;Out \: of \: the\: plane \\ (c)\; Up \: the\: plane & \quad (d)\;Down\: the\: plane \end {array}$