A certain stadium is currently full to \(\frac{13}{16}\) of its maximum seating capacity. What is the maximum seating capacity of the stadium?
(1) If 1,250 people were to enter the stadium, it would be full to \(\frac {15}{16}\) of its maximum seating capacity.
(2) If 2,500 people were to leave the stadium, it would be full to \(\frac {10}{16}\) of its maximum seating capacity.
In the two triangles, what is the value of \( P + Q + R + S \)?
I. \( A + B = 90^\circ \)
II. \( P + Q = R + S \)