Answer Happy

A man has built a roller coaster in a loop-de-loop. If heis launched at 30m/s, what would the magnitude of his normalacceleration be at the top of the loop? The loop is 40m talland has a radius of 20m at the top. Gravity is 10m/s^2 downon the man's planet. Answer in m/s^2 to three sig.figs.
Use Particle Work energy, NOT momentum equations, thank you!