A pirate ship traveling along a river (yes, river pirates are a thing) that flows to the West with speed 17.3 m/s sails downriver (West) with a speed 13.8 m/s with respect to the river. It has a cannon that only fires cannonballs perpendicular to the direction the boat travels (in this case, North) with-speed 81.6 m/s with respect to the boat. What is the speed of a cannonball fired from this boat as measured by an unfortunate observer on the ground?