A difficult question!! Intelligent people, answer!!?

Imagine that the world has a completely flat surface around the equator. Suppose, a very lon as long as the cirference of the Earth is laid from any middle point in the equator and stretches back to the point where it started,but the string used was longer by 5 feet than the exact cirference of the Earth around the equator. Now, how far will the string be above from the ground if the string is measured evenly above the ground?