A model rocket is launched at 62 degrees above the horizontal with an initial speed of 28m/s. the rocket travels for 4.5s along its initial line of motion with a constant acceleration of 13 m/s^2. At this time, the engine of the rocket stops and the rocket proceeds to move as a projectile. Ignore asked resistance.

Find the maximum altitude the rocket reaches. I got 31.2 using the v=vo^2 +2ad formula with v=0, v0= 28sin62, and a=-9.8. However the answer key says 530m. What did I do wrong?

Also, how would I find the total time the rocket is in the air?