A proton is released such that its initical velocity is from right to left across this page. THe proton's path, however, is deflected in a direction toward the bottom edge of the page due to the presence of a uniform magnetic field. What is the direction of the magnetic field

the magnetic field is leaving the sheet

Explanation:

The magnetic force is given by the expression

        F = q v x B

where bold letters indicate vectors, the modulus of this expression is

       F = q v B sin θ

the direction of the force is given by the right hand rule, for a positive charge

the thumb indicates the direction of the speed, in this case from right to left

the palm the direction of the force, in our case upwards

the fingers extended the direction of the magnetic field, this case after fixing the other two components it points out of the blade

In short the magnetic field is leaving the sheet