8. An object moves on a horizontal coordinate line. Its directed distance s from the origin at the end of t seconds is s(t) = 13 -912 + 24t - 16 feet. (a) when is the particle moving to the left? (b) what is the acceleration when its velocity is equal to zero? (c) when is the acceleration positive? (d) when is the particle slowing down? (e) what is the total distance travelled by the particle after 4 seconds? 9. A woman standing on a cliff is watching a motor boat as the boat approaches the shoreline directly below her. If the woman's eyes are 250 feet above the water level and if the boat is approaching at 30 feet per second, how fast is the angle of depression of the boat from the woman's eyes changing when the boat is 250 feet from the shore? 10. A right circular cone with radius 3 cm and height 6 cm is submerged point first into a tall cylinder of radius 5 cm that is partially filled with water. How fast is the water level rising when the cylinder is completely submerged