A. What is the shortest time that a jet pilot starting from rest can take to reach Mach-3.4 (four times the speed of sound) without graying out? (Use 331m/s for the speed of sound in cold air.)

This is what I did but I keep getting it wrong:
a=4g=4(9.81m/s^2)=29.43m/s^2
v=4 x 331m/s=1324 m/s

then used equation:

to solve for t which yields: y=  

 

B. How far would the plane travel during this period of acceleration?

I used equation to solve for Δy:

solving it:

which is 22.28km (the answer is supposed to be in km)
 

v = v + at Vo