To find area $ A $ use formula:
$$ A = a \cdot b $$After substituting $ a = \frac{ 13 }{ 2 } $ and $ b = \frac{ 13 }{ 4 } $ we have:
$$ A = \frac{ 13 }{ 2 } \cdot \frac{ 13 }{ 4 } $$$$ A = \frac{ 13 }{ 2 } \cdot \frac{ 13 }{ 4 } $$$$ A = \frac{ 169 }{ 8 } $$