25 The diagram shows the speed-time graph of car A. (a) Find the acceleration of car A when t = 7. (b) Find an expression, in terms of k, for the distance moved by car A between t = 0 and t = k, where k > 10. Give your answer in its simplest form. (c) Car B travels at a constant speed of 12 m/s in the same direction as car A. (i) On the diagram, sketch the speed-time graph of car B. (ii) When t = 0, car B passes car A. When t = k, car A overtakes car B. Find the value of k.