Can someone answer all parts? ? extra points for this one!

     a) 
Acceleration of stone = 10 

Integrate: 
So velocity = 10t 

Integrate again: 
So distance from starting point = 5t^2 

Distance from ground = 450-5t^2 

b) 
450 - 5t^2 = 0 

9.48 seconds 

c) velocity = 10t 

Put the time into this to give: 

94.8 m/s 

d. 

Velocity = 10t + 5 

Integrate again: 

5t^2 + 5t 

Solve 
5t^2 + 5t = 450 

Gives 9 seconds

The velocity is 0t, here's how I got this answer

To find Velocity you must do dv/dt, so in this case it would look like this:

DV/DT = -9.8 which also equals V = -9.8t + C so in this case the Velocity would be 0 because -9.8 - (-9.8) = 0