Step 1: Read the values (in \$ million) from the chart.
Yahoo (Y): \(Y_4=250,\; Y_5=600,\; Y_6=1200\).
Facebook (F): \(F_4=300,\; F_5=750,\; F_6=2000\).
Step 2: Compute percentage increases.
Yahoo: \( \frac{600-250}{250}=140%, \frac{1200-600}{600}=100%\).
Average for Yahoo \(=\frac{140%+100%}{2}=120%\).
Facebook: \( \frac{750-300}{300}=150%, \frac{2000-750}{750}=166.\overline{6}%\).
Average for Facebook \(=\frac{150%+166.\overline{6}%}{2}=158.\overline{3}%\).
Step 3: Difference \(=158.\overline{3}%-120%=38.\overline{3}%\approx 40%\).
\[
\boxed{40%}
\]