SP1. A railroad engine moves forward along a straight section of track for a distance of 70 m due west at a constant speed of 5 m/s . It then reverses its direction and travels 32 m due east at a constant speed of 4 m/s . The time required for this deceleration and reversal is very short due to the small speeds involved. a. What is the time required for the entire process? b. Sketch a graph of average speed versus time for this process . Show the deceleration and acceleration upon reversal as occurring over a very short time interval . c. Using negative values of velocity to represent reversed motion, sketch a graph of velocity versus time for the engine ( see fig. 2.15 ). d. Sketch a graph of acceleration versus time for the engine (see fig . 2.16).