To stretch an ideal spring 9.00 cm from its unstretched length, 18.0 J of work must be done. What is the force constant of this spring? Express your answer with the appropriate units. k = Value Units Submit Request Answer Part B What magnitude force is needed to stretch the spring 9.00 cm from its unstretched length? Express your answer with the appropriate units. F = Part C How much work must be done to compress this spring 4.00 cm from its unstretched length? Express your answer with the appropriate units. W = Submit Request Answer Part D What force is needed to compress the spring this distance? Express your answer with the appropriate units. F =