Easy physics question~!?

[Soda Tears]

A 50kg passenger in a car is held firmly by her seatbelt during a collision. The seatbelt, in stopping her, puts an average force of 12 000N on her for 0.01s. Calculate:

a) the impulse of the force

The formula for impulse is I=Ft or is it F=(mv-mu)/t ??

b) the initial speed of the car

Any help at all will be much much much appreciated. I'm trying to love physics but its not very easy.. :S

[THE MAN]

(a)
Impulse is defined as

Impulse = Average force x time

With F = m x a this is equal to

Impulse = mass x average acceleration x time = mass x change in velocity

(b)
Assume that the final speed is zero.