A solution mine for nacholite that is processed into soda ash is developed by wells 1,800 ft below the surface in the Piceance basin of Colorado. The mine will produce about 1 million short tons per year initially. Assume the “pay zone” is 90 ft thick, dips 5◦ and that dissolvable nacholite is 20% of the of the zone material, then (1) specify an appropriate subsidence factor and angle of draw; (2) estimate the maximum subsidence; (3) critical width, and (4) trough width at the time mining extends to the critical area limit.