21. Two canoes are 8 m apart on a lake. Each bobs up and down with a period of 2.3 s. When one canoe is at its highest point on a wave in the lake, the other canoe is at the lowest point. Both canoes are always within a single cycle of the waves. Determine the speed of the waves. a. 7.0 m/s b. 10 m/s c. 14.1 m/s d. 3.6 m/s