Angle = 68⁰ is an inscribed angles, this angle equal 68⁰,
so it intersect arc = 2*68⁰= 136⁰.
Arc of the whole circle (circumference) =360⁰,and it also =b+104+136.
b+104+136 =360
b=360-(104+136) = 120⁰
Answer A. b=120⁰.
