A rock thrown vertically upward from the surface of the moon at a velocity of 4 m/sec reaches a height of s = 4t - 0.81 meters in t sec. a. Find the rock's velocity and acceleration at time t. b. How long does it take the rock to reach its highest point? c. How high does the rock go? d. How long does it take the rock to reach half its maximum height? e. How long is the rock aloft? a. Find the rock's velocity at time t. V= m/s