Please Help a Desperate Physics Student?

When they go swimming in their favorite water hole, Jeb and Dixie like to swing over the water on an old tire attached to a tree branch with a 3.0 m long rope. If the diameter of the rope is 2.00 cm by how much does the rope stretch when a 60.0 kg Dixie swings from it. (Ynylon=3.7*10^9 N/m^2)