A train travels 84 km/h when it reaches a slower train 47 meters ahead traveling the same direction at 24 km/h. If the faster train decelerates at 2.1 m/s^2 while the slower train is at a constant speed, when will they collide? If the train that is faster begins to decelerate at 2.1 m/s^2 while the slower train continues at a constant speed, what will be the relative speed in which they will collide?

I got 8.5 seconds for the first one and 3.68 seconds for the last one. Thanks Y'all.