Physics question: Kinetic Energy!?

[Soda Tears]

A 12kg car, at rest, is acted upon by a force acting towards the north, for 5s. This changes its kinetic energy by 2400J.

There are some questions for this statement, but I've done them. It connects to the next question:

If the car had been moving at 10m/s south initially, and the same force acted on it for the same time, calculate:

a) the initial kinetic energy of the car

I've done this, its 600J.

b) the work done on the car by the force

Um, I have a problem with this question.. Is the work done like.. 600J or 2400J? I guess its 2400J right?

c) the final kinetic energy of the car
Formula is Ek=1/2mv^2 but which values do I use?


Thanks so much! Any help will be appreciated!