I'm guessing that you need the force, since the question doesn't specify I'll just use the force equation. If this is not what you wanted let me know in the comments section of this answer.
- m = 300 kg (kilograms)
- a = 4 (m/(s^2)) (meters per second square)
- F = ma
- F = 300 x 4
- F = 1200 N (newtons)