The area (in square units) of the region enclosed by the ellipse \( x^{2}+3y^{2}=18 \) in the first quadrant below the line \( y=x \) is
\( \sqrt{3}\pi \)
\( \sqrt{3}\pi+\frac{3}{4} \)
\( \sqrt{3}\pi+1 \)
\( \sqrt{3}\pi-\frac{3}{4} \)