A stone thrown downward with an initial velocity of 34.3 m/sec will travel a distance of s meters, where s(t) = 4.9t^2 + 34.3t and t is in seconds. If a stone is thrown downward at 34.3 m/sec from a height of 588 m, how long will it take the stone to hit the ground? Round your answer to the nearest second.

If anyone can help explain how to solve this problem I would be extremely grateful.