Model of a projectile

A projectile is launched from a tower into the air with an initial velocity of 48m/s. Its height (h), in metres, above the ground is modelled by: h=-16t^2+v_0 t+64 where t is time in seconds and v_0 is the initial velocity. Using the GeoGebra file below and your knowledge of quadratic equations: How long was the projectile in the air? When did it reach its maximum height? What was its maximum height?