Civil engineers are designing a section of road that is going to dip below sea level. The road's curve can be modeled by the equation y = 0.00005x^2 - 0.06x, where x is the horizontal distance in feet between the points where the road is at sea level and y is the elevation. The engineers want to put stop signs at the locations where the elevation of the road is equal to sea level. At what horizontal distances will they place the stop signs?