A skydiver is falling to earth.  When he is traveling at 51.3 m/sec, he opens his parachute, and after 3.00 seconds he reaches the speed of 4.30 m/sec.  The remaining 60 seconds before landing is spent traveling downward at the speed of 4.30 m/sec.  What is his acceleration 30 seconds before landing?

his speed was constant at 4.30m/s, and therefore acceleration was zero.