What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_15, if x_15 were an office clerk, then x_15 is playing a game. For all x_15, x_15 will play squash or x_15 will write a letter. For all x_15, if x_15 takes a plane, then x_15 is climbing a mountain. For all x_15, x_15 is an office clerk if and only if x_15 will write a letter. There is at least one x_15 for which if x_15 plays a game, then x_15 is climbing a mountain. For all x_15, x_15 will not play squash or x_15 will take a plane.
There is at least one x_15 for which if x_15 were an office clerk, then x_15 is climbing a mountain. For all x_15, x_15 will write a letter or x_15 will take a plane. For all x_15, if x_15 were an office clerk, then x_15 is writing a letter. For all x_15, if x_15 writes a letter, then x_15 is an office clerk.