Please show calculations

A cannonball is fired horizontally off the edge of a 10 m high cliff, with a speed of 20 m/'s. 10m a.) Find the time it takes for the cannonball to hit the ground. b.) How far from the base of the cliff does the ball land? c.) Find the total velocity vector of the cannonball just before it hits the ground. d.) If you wanted to make the cannonball's flight time to be exactly 1.6 seconds, then you could dig a hole in the ground below the cliff (at the appropriate location.) How deep would this hole need to be