Required area = (Area of semi circle AC - Area of semi-circle AB) + (Area of semi-circle BE - Area of semi circle CD) + (Area of semi-circle DE) = \( \Large \left[ \frac{1}{2} \pi \left(\frac{10.5}{2}\right)^{2}-\frac{1}{2} \pi \left(\frac{7}{2}\right)^{2} \right] \) \( \Large + \left[ \frac{1}{2} \pi \left(\frac{17.5}{2}\right)^{2} - \frac{1}{2} \pi \left(\frac{7}{2}\right)^{2} \right] + \frac{1}{2} \pi \left(\frac{7}{2}\right)^{2} \) = \( \Large \frac{ \pi }{2}\left[ \left(\frac{10.5}{2}\right)^{2}+ \left(\frac{17.5}{2}\right)^{2}- \left(\frac{7}{2}\right)^{2} \right] \) = \( \Large \frac{ \pi }{8}\left[ \left(10.5\right)^{2}+ \left(17.5\right)^{2}- \left(7\right)^{2} \right] \) = \( \Large \frac{ \pi }{8}\left[ \left(10.5\right)^{2}+ \left(10.5\right) \left(24.5\right) \right] \) = \( \Large \frac{ \pi }{8}\left[ \left(10.5\right) \left(35\right) \right] \) = \( \Large \frac{ \pi }{16} \left(35\right) \left(21\right) cm^{2} \)
