Counting tuples satisfying a tuple relational calculus formula

Let there be two relations $X$ and $Y$ as shown. $X$ has three columns $P$, $Q$ and $R$. $Y$ has two columns $P$ and $S$.

| $X.P$ | $X.Q$ | $X.R$ | |—|—|—| | P1 | Q1 | R1 | | P2 | Q2 | R2 | | P3 | Q3 | R2 |

| $Y.P$ | $Y.S$ | |—|—| | P1 | 10 | | P1 | 15 | | P2 | 20 | | P3 | 1 |

Consider that the following tuple relational calculus expression is evaluated. $$\{t \mid t \in X \wedge \exists z \in X(t[P] = z[P]) \wedge \exists m \in Y \, (m[P] = t[P] \wedge m[S] > 1)\}$$ The number of tuples that will be returned is __________ . (Answer in integer)