21. • IP An 85-kg lumberjack stands at one end of a 380-kg floating log, as shown in Figure 9-17. Both the log and the lumber-jack are at rest initially.

(a) If the lumberjack now trots toward the other end of the log with a speed of 2.7 m/s relative to the log,what is the lumberjack's speed relatíve to the shore? Ignore friction between the log and the water. (b) If the mass of the log had-been greater, would the lumberjack's speed relative to the shore be greater than, less than, or the same as in part (a)? Explain.(c) Check your answer to part (b) by calculating the lumber-jack's speed relative to the shore for the case of a 450-kg log.