Determine the velocity of the stone when it returns to the height from which it was thrown.
Choose the initial point where the stone is launched and the final point when it passes thee position coming down
Substitute known values into the following equation:

vᵧc² = vya² + 2aᵧ, (yc - ya )
vᵧc² = ( 19.0m/s2)2 + 2(-9.80 m/s²) ( 0 - 0 ) = 361 m²/s²
vᵧc = _________ m/s