A cylindrically shaped piece of collagen (a substance found in the body in connective tissue) is being stretched by a force that increases from 0 to 0.0436 N. The length and radius of the collagen are, respectively, 2.90 cm and 0.0815 cm, and Young's modulus is 3.1 x 106 N/m2. (a) If the stretching obeys Hooke's law, what is the spring constant k for collagen? (b) How much work is done by the variable force that stretches the collagen?