How much time elapses before the two kittens collide

6.8 s

Explanation:

Let's say the west end of the field is position 0 m and the east end of the field is position 250 m.

The position of kitten A is:

x = 0 + 25 t

And the position of kitten B is:

x = 250 - 12 t

The kittens collide when they have the same position:

25 t = 250 - 12 t

37 t = 250

t ≈ 6.8 s

c) up is the direction the magnetic force is acting on the charge.

i'm on my way to history not a mistory.