A 34-Kg Child on an 18-Kg Swing Set Swings Back

Multiple Choice

A 34-kg child on an 18-kg swing set swings back and forth through small angles.If the length of the very light supporting cables for the swing is 4.9m.
How long does it take for each complete back-and-forth swing? Assume that the child and swing set are very small compared to the length of the cables.

A) 4.4 s
B) 4.8 s
C) 5.3 s
D) 5.7 s