A rock is thrown off of a 100 foot cliff with an upward velocity of 45 m/s. As a result its height after t seconds is given by the formula: h(t)= 100+45t-5t^2

Question

A rock is thrown off of a 100 foot cliff with an upward velocity of 45 m/s. As a result its height after t seconds is given by the formula: h(t)= 100+45t-5t^2
 
The height after 6 seconds is 190

What is the velocity after 6 seconds?