(a) forces both pointing into the plane of the paper
For the given figure, the proton and electron are moving in opposite directions to each other and is perpendicular to the direction of magnetic field. Now, we know that the direction of current is taken opposite to the direction of motion of electron. So, both electron and proton have current in same direction. Therefore, the forces acting on them are given by Fleming s left hand rule and they are pointing into the plane of the paper.