You are the Industrial Engineering technologist for JMPD and your supervisor has asked you to determine the most desirable setting for a series of three traffic signals on a two kilometer strip of access road into Braamfontein. Applying your knowledge of work-study, you then devise a timing system to enable you to observe the number of vehicles going through all three signals without stopping or vehicles rushing a yellow signal. The data you collected is presented in the table below: Boundaries 15.5-18.5 18.5-21.5 21.5-24.5 24.5-27.5 27.5-30.5 30.5-33.5 33.5-36.5 36.5-39.5 Determine: Midpoint 17 20 23 26 29 32 35 38 Frequency 12 613282T 10 20 a) Average b) Three (3) Standard Deviation c) Variance for data d) The percentage of cars going through the signals during the 22nd and 29th time setting [20] (5) (5) (2) (8)