Evaluate ∫∫xy dxdy over the region bounded by x axis, ordinate x=2a and the curve x2=4ay.

• A. \(\frac{a^4}{3} \)
• B. \(\frac{a^4}{6} \)
• C. \(\frac{a^3}{3} \)
• D. \(\frac{a^2}{6} \)