A 34-Kg Child on an 18-Kg Swing Set Swings Back $4.9 \mathrm {~m}$

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 $4.9 \mathrm {~m}$ 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