You have a light spring which obeys Hooke's law. This spring stretches 2.66 cm vertically when a 2.70 kg object is suspended from it. Determine the following. (a) the force constant of the spring (in N/m).

(b) the distance (in cm) the spring stretches if you replace the 2.70 kg object with a 1.35 kg object.

(c) the amount of work (in J) an external agent must do to stretch the spring 8.40 cm from its unstretched position.