6 A dog runs past a tree when t = 0 with the speed of 3.7ms-1. It accelerates for 5 seconds so that its speed satisfies v = (u + 0.4t) ms-1. a Write down the value of u. For the next 5 seconds, the dog decelerates and its speed satisfies: 142.5 U = ms 1 b Find the dog's final speed. c Find the dog's final displacement from the tree. d After how long is the dog 32 m from the tree