vr          vt
 Pitch type     spin direction    (mph)       (mph)          S
----------------------------------------------------------------------------
  fastball        backspin        19.0         90                

  changeup        backspin        11.2         80                 

  curve           topspin         11.2         80                
----------------------------------------------------------------------------


  Once we have "S", we can determine the lift parameter CL,
  and then we'll finally be able to compute the Magnus force.

  Q:  Can you compute the spin parameter S?