It seems like the region $A$ was not fully defined in your question. You started with $A = \{(x, y) | 0$ but did not complete the description of the region $A$.

To help you effectively, could you please clarify the exact region $A$? For instance, are you defining a specific range for $x$ and $y$ within the unit square $[0, 1] \times [0, 1]$, such as:

• $A = \{(x, y) | 0 \leq x \leq a, 0 \leq y \leq b\}$ for some $a$ and $b$?
• Or is it another specific region like $A = \{(x, y) | x + y \leq c\}$ for some constant $c$?

Let me know the precise definition of $A$, and I'll calculate $P[(x, y) \in A]$ for you.