In Sec. 14–10, Eq. (a) is given for Ks based on the procedure in Ex. 14–2. Derive this equation. A speed-reducer has 20◦ full-depth teeth, and the single-reduction spur-gear gearset has 22 and 60 teeth. The diametral pitch is 4 teeth/in and the face width is 3 ¼ in. The pinion shaft speed is 1145 rev/min. The life goal of 5-year 24-hour-per-day service is about 3(109) pinion revolutions.