The x component of velocity (i term) is constant. The y component, vy = vy0 - gt. You know t and vy (j term), so you can solve for vy0. Once you know vy0 you can solve for
A) R = (v02/g)sin(2θ0) (Use pythagorean theorem to solve for v0 and tan-1(vy0/vx0) to solve for θ0)
B) H = vy02/(2g)
C) The speed with which it will be going at ground level will be |v0 | (It is a symmetric launch)
D) The angle will be -θ0
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