mechanics question heLPPP

Hello if someone could help me with the following question I would be really grateful.

-->The ends of an elastic string of natural lenght 2l and modulus λ are attached to two pegs a distance 4l apart.The string is held firmly at its midpoint H,and this point is then moved along the line between the pegs.Find expressions for the force needed to hold it steady at a distance x from its original position
a) x< l
b)l<x<3l
c)x>3l