Need help to sole this kinetic homework?

Car A is 600 m from the centre of the intersection when it starts from rest and accelerates uniformly at 4m/ss. Reaching a speed 0f 24m/s that it maintains. Art the instant car A take off, car B IS 780 m from the centre of the intersection and travelling at a constant speed of 28m/s. When car B is 53 m from the centre of the intersection it decelerates uniformly at 5m/ss.

a. Which car gets to the centre of the intersection first?

b. How far past the centre of the intersection is the first car when the second car reaches it?

c. If all other condition remains the same, what constant acceleration would:

- The second car needs to have for a collision to occur?

- The first car needs to have for a collision to occur?

I have done the question a and b …but I don’t know how to do question c. Anyone help me?

the result for a is

a. t (A)= 28 second.

t(B)= 28.35 second.

so car A comes first.

b. it's 8 m from the intersection to the first car.

c. ???? i know the answer but i don't know how to work out ...it's

- a= -2m/ss

- a= 3.58m/ss

Can anyone help me with question c? please ...