What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all z_4, if z_4 were a mechanic, then z_4 is making tea. For all z_4, z_4 is a mechanic or z_4 is not happy. For all z_4, if z_4 writes a letter, then z_4 is happy. For all z_4, if z_4 makes tea, then z_4 is a mechanic.
For all z_4, if z_4 were happy, then z_4 is a mechanic. For all z_4, z_4 is a mechanic if and only if z_4 will make tea. For all z_4, z_4 will make tea if and only if z_4 is a mechanic.