The height h (in feet) above the water of a cliff diver is modeled by h=-16h^2+8t+80, where t is the time (in sec). how long is the diver in the air?

The height h (in feet) above the water of a cliff diver is modeled by h=-16h^2+8t+80, where t is the time (in sec). how long is the diver in the air?