[10] 3. If a rock is thrown upward on the planet Mars with a velocity of \( 10 m / s \) , its height (in meters) after \( t \) seconds is given by
\( H = 10 t - 1.86 t ^ { 2 } \)
a) Find the velocity of the rock after \( 1 \) second b) Find the velocity of the rock when \( t = a \) c) When will the rock hit the surface of the planet? d) With what velocity will the rock hit the surface?