What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_10, if x_10 were a sailor, then x_10 is writing a letter. If John makes tea, then Mary is writing a letter. It is sunny or Mary is a sailor. If it is sunny, then John is making tea.
If it is sunny, then Mary is writing a letter. If Mary plays squash, then it is sunny.