suppose that a projectile is fired straight upward from the surface of the earth with initial velocity v0 and assume its height y(t) above the surface satisfies the initial value problem: y''=-GM/(y+R)^2-b*e^(-ay), y(0)=0, y'(0)=v0. Compute the maximum altitude the projectile reaches and the time (from launch) for the projectile to reach the maximum altitude. In the above, G,M,R,v0,a,b are all given constants.