A volcano erupts 50m below the sea level. A rock leaves the crater at 20 m/s at an angle 30 deg with the vertical line. The rock has a mass of 15kg. IGNORE WATER RESISTANCE. It gets out of the water, reaches a max height and falls back it.
When does it reach 30 below sea for the first and second times?
$a = <0, -9.8>$
$v = <20sin(30), -9.8t+20cos(30)> = <10, -9.8t+17.32>$
$s = <10t, -4.9t^2+17.32t>$
For the object to be 30m below sea level, y=20m, so $s_y=20 \implies -4.9t^2+17.32t-20=0$.
However, no real solutions exist to this. This is so simple, I apologize for asking, but what am I overlooking?