After grouting, a cemented fill, that has completely filled the old workings, has a Young’s modulus of 100ksi (690 MPa), and an unconfined compressive strength of 3,400 psi (23.4 MPa), as determined from unconfined compressive strength tests. The original extraction ratio in this area is estimated to be about 40%. Assume that the old pillars deteriorate to the point where they have no support capability. Estimate the maximum subsidence that might occur in this event. Explain why this is a maximum or upper bound estimate and why the actual “settlement” would probably be less. Or is it?