A box with mass M=70kg is tired to a rubber rope and dropped off a bridge which is at height H=100m above the ground. The rope has non-stretch length l=10m and cross-section area A=60cm^2. If the lowest height that box reaches is h=10m (before it is pulled back up by the elastic rope). Find the young modulus of the rubber y=?Gravitational acceleration is g=10m/s^2