This question involves two parts. 1. translate the argument provided in this prompt into formal logic and then use the truth-tree decision procedure (relying on proof tools or pencil/pen and paper) to determine whether the argument is deductively valid or invalid (entailment/non-entailment). 2. if the argument is invalid (a case of non-entailment), determine an assignment of truth values (interpretation) to the propositional letters that would show the argument to be invalid. here is the argument: if paul and sally arrived on time, then qbert or ron were there to greet them. qbert or ron were there to great them. therefore, either paul or sally arrived on time.