\frac{P_{ABCD}}{P_{EFGH}} = \frac{|VV'|^2}{|VV''|^2} \\
\frac{15^2}{P_{EFGH}} = \frac{10^2}{6^2} \\
\frac{225}{P_{EFGH}} = \frac{100}{36} \\
100P_{EFGH} = 8100 \\
P_{EFGH} = 81\,cm^2