A projectile is fired straight upwards with a vertical position function of s(t) = 50t - 4.9t2 + 20 where s is in metres and t is in seconds. a. What is the projectile's initial vertical position and initial vertical velocity? b. What is the projectile's acceleration? c. When does the projectile reach maximum height? d. When does the projectile reach a height of 75% of its maximum height for the first time