physics
posted by Gail .
Suppose a stone is thrown at an angle of 30 degrees below the horizontal, if it strikes the ground 57m away, find (a)the time of flight, (b)the initial speed, and (c) the speed and the angle of the velocity vector with respect to the horizontal impact.

If it is thrown 30 degrees below horizontal, on level ground, it strikes the ground right away.
Are you sure you copied the problem correctly? 
yes the question was copied correctly.

How high is the stone when thrown?

There was no height given and no other info given for this problem. Per the textbook, the answers are (a) 1.57sec (b) 41.9m/s (c) 51.3m/s and 45 degree angle. But I can't figure out how the answers were calculated?

Nor can I.