Two Children Setup a "Telephone" by Placing a Long, Slender

Multiple Choice

Two children setup a "telephone" by placing a long, slender aluminum (Y = 6.9 × 10¹⁰ N/m²) rod that has a length of 6.1-m between their two houses. To communicate, a child taps a coded message on one end. How long do the sound waves take to reach the other end? Note: the density of aluminum is 2700 kg/m³.

A) 1.2 × 10^-3 s
B) 2.4 × 10^-7 s
C) 8.0 × 10^-6 s
D) 6.3 × 10^-5 s
E) 1.1 × 10^-4 s