In a trapezium $\text{ABCD},\; \text{AB}$ is parallel to $\text{DC}, \; \text{BC}$ is perpendicular to $\text{DC}$ and $\angle \text{BAD} = 45^{\circ}.$ If $\text{DC} = 5 \; \text{cm}, \; \text{BC} = 4 \; \text{cm},$ the area of the trapezium in $\text{sq. cm}$ is