Our teacher frequently gives some hard items for us. Attached is the image. All equations needed for this are the 4 kinematic eqs, and their variations.

The problem: A rifle is mounted on top of a building of height H. It is fired and has a constant horizontal speed of 340 m/s. After travelling a certain distance D, it hits a window 0.5m above the ground and travels another 6.9 m before hitting the ground.

Question: How long is H and D?

My answers reached up to the 11,000m (which I saw was wrong, I just wanted to have somthing to submit). I consulted him after and he gave me the answers. Was wondering if anyone here could actually solve it. I'll give him the answers he gave me if anyone actually gets it or asks for it.