Consider the following premises. For all x_10, if x_10 were a mechanic, then x_10 is drinking water. David is not rich. David is rich if and only if Michael is drinking water. Can we infer the following from them? Michael is not a mechanic.
 From the fact that for all x_10, if x_10 were a mechanic, then x_10 is drinking water we can infer that if Michael were a mechanic, then Michael is drinking water. From the fact that David is rich if and only if Michael is drinking water, and that David is not rich we can infer that Michael is not drinking water. Finally, from the fact that if Michael were a mechanic, then Michael is drinking water, and that Michael is not drinking water we can infer that Michael is not a mechanic. Therefore, the answer is yes.