1103020804

In the parallelogram $ABCD$ shown in the picture, $G$ is the midpoint of $CD$, $F$ is the midpoint of $BC$ and $\overrightarrow{u}=\overrightarrow{CG}$, $\overrightarrow{v}=\overrightarrow{CF}$, $\overrightarrow{a}=\overrightarrow{AD}$ and $\overrightarrow{b}=\overrightarrow{AC}$. Express vectors $\overrightarrow{a}$ and $\overrightarrow{b}$ as a linear combination of vectors $\overrightarrow{u}$ and $\overrightarrow{v}$.