Answer:
The velocity is 
Explanation:
From the question we are told that
The first distance is 
The first speed is 
The second distance is 
The second speed is 
Generally the time taken for first distance is



The time taken for second distance is



The total time is mathematically represented as

=> 
=> 
Generally the constant velocity that would let her finish at the same time is mathematically represented as

=> 
=> 
A.gold is the answer. As it's density is 19.32 grams per cubic centimeter which is lot more than the other substances.
Sound energy is produced when an object vibrates so an example would be a telephone ringing or someone playing a bass guitar
Answer = 6.24x10^18 x ((2 x 3600) + (47 x 60) + 10)