Translate the following inference to logic notation: There is at least one x for which x_7 is a mechanic or x_7 will drink water. For all x, x_7 will drink water if and only if x_7 will play tennis. For all x, x_7 is a mechanic if and only if x_7 will play tennis. Therefore there is at least one x for which x_7 will play tennis.
exists x: P(x) or Q(x). forall x: Q(x) <-> R(x). forall x: P(x) <-> R(x). Therefore exists x: R(x).