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Diameter = 2 r
     14 cm = 2 r
       7 cm = r

Luas juring = 72°/360° x 7 x 7 x 22/7
                   = 1/5 x 7 x 7 x 22/7
                   = 1/5 x 154
                   = 30,8 cm² (C)