a heavy sphere is thrown 45 degrees upwards. it spends twice as long descending as ascending, because it's been thrown off a 30-metre-high cliff. it then hits the ground, and with each bounce loses 80% of its energy. will the ball hit someone standing 70metres from the cliff?

assume g = 10 m/s/s

this is all the question says. i think i've worked out the initial speed, but i'm not sure

i am also assuming no air resistance, each time the ball hits the ground the collision is elastic, and that the person standing 70m away is infinitely tall, so that the ball cannot bounce over

thanks