Four wires with currents are arranged in the corners of a square. Current in the upper left corner (as viewed from your point of view) is 2I, all others are I. Direction of all currents is out of a page (towards you). The direction of net magnetic field in the center of a square is:
a. towards the upper right corner
b. towards the upper left corner
c. towards the lower right corner
d. towards the lower right corner
e. magnetic field is zero in the center

a I.e

 towards the upper right corner

Explanation:

A wire carrying electric current will produce a magnetic field with closed field lines. In the direction of the current, and the fingers curl in the direction of the magnetic field loops  

If we take the four sides of square as four separate current carrying wires , if we apply Fleming's left hand rule to find the force on each side , we find that ,forces will not be equal due to un even value of current.

magnetic force on each side will be

F = ILBsin 90

Making B the subject of the formula, we will found out that its direction will move towards the upper right corner

Well, to find velocity, you need to divide the change in position by the change in time. So on your graph, find two points. Find the change in position and time in those two points, these can be any two points on the graph. Then you can divide the change in position by the change in time. (I know this explanation is confusing so hopefully what I included below can help.)

Velocity =   x1 - x2  divided by t1 - t2

x1 = final position   x2 = initial position

t1 = final time          t2 = initial time

Hopefully this helps!