(N/A) An umbrella has $8$ ribs,which divide the circular area into $8$ equal sectors.
The angle subtended by each sector at the center is $\theta = \frac{360^{\circ}}{8} = 45^{\circ}$.
The radius of the circle is $r = 45 \, cm$.
The area of a sector is given by the formula: $\text{Area} = \frac{\theta}{360^{\circ}} \times \pi r^{2}$.
Substituting the values:
$\text{Area} = \frac{45^{\circ}}{360^{\circ}} \times \frac{22}{7} \times (45)^{2}$
$\text{Area} = \frac{1}{8} \times \frac{22}{7} \times 2025$
$\text{Area} = \frac{11}{4 \times 7} \times 2025 = \frac{11 \times 2025}{28}$
$\text{Area} = \frac{22275}{28} \, cm^{2} \approx 795.54 \, cm^{2}$.