What is the Recoil Speed?

A cannon on a railroad car is facing in a direction parallel to the tracks (the figure below). It fires a 98 kg shell at a speed of 105 m/s (relative to the ground) at an angle of 60.0� above the horizontal. If the cannon plus car have a m of 5.4 multiplied by 104 kg, what is the recoil speed of the car if it was at rest before the cannon was fired? [Hint: A component of a system's momentum along an axis is conserved if the net external force acting on the system has no component along that axis.]