Using the diagram, v is 0.840 m/s, h1=0.400 m and h2=0.230 m. Please hep!! i desperatly need to pass the test

Using the diagram, v is 0.840 m/s, h1 is 0.400 m and h2 is 0.230 m.
Calculate the speed of the car at point b.

heres the link: http://www.flickr.com/photos/62137592@N03/5700213813/in/photostream/
Please help!!

If the surface is frictionless, the car will lose potential energy and that potential energy will b converted to its kinetic energy.(conservation of mechanical energy)

Change in kinetic energy = change in potential energy

(1/2) m ((vf)^2 - (vi)^2) = mg(h1)
=>(vf)^2 - (vi)^2 = 2g(h1)
=>(vf) =sqrt( (vi)^2 + 2g(h1) )
=>(vf) =2.92 m/s