A 7.2-kg bowling ball is attached to the end of a nylon cord with a cross-sectional area of 3.75 x10^-5 m2. The other end of the cord is fixed to the ceiling. When the bowling ball is pulled to one side and released from rest, it swings downward in a circular arc. At the instant it reaches its lowest point, the bowling ball is 1.6 m lower than the point it was released from, and the cord is stretched 2.51 x10^-3 m from its unstrained length. What is the unstrained length of the cord? Hint: When calculating any quantity other than the strain, ignore the increase in the length of the cord.