\[\boxed{\mathbf{1024\ (1024)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ а)\ S = 3 \bullet 4 = 12\ см^{2}.\]
\[\textbf{б)}\ S = 4 \bullet 5 = 20\ см^{2}.\]
\[2)\ S = a \bullet h.\]