A cyclist sets off from rest and accelerates uniformly to a speed of 8 m/s over the first 4 seconds of her journey. She then travels at this constant speed for a further T seconds, before decelerating uniformly to rest over the next 5 seconds. The velocity-time graph for her journey is shown below. Given that the total distance she travels is 100 m, find the value of T.
Figure (to be drawn): Velocity-time graph: velocity (m/s) on the vertical axis, time (s) on the horizontal axis, starting at the origin (0, 0). A straight line rises from (0, 0) to (4, 8). A horizontal line continues from (4, 8) to (4+T, 8). A straight line then falls from (4+T, 8) to (4+T+5, 0), meeting the time axis there.
(Total for Question 19 is 4 marks)