When a 2.00-kg object is hung vertically on a certain light spring described by Hooke's law, the spring stretches 3.17 cm.

(a) What is the force constant of the spring?
N/m

(b) If the 2.00-kg object is removed, how far will the spring stretch if a 1.00-kg block is hung on it?
. cm

(c) How much work must an external agent do to stretch the same spring 8.50 cm from its unstretched position?