tolong secepat nya please.....

iv. K = Keliling lingkaran besar × 1/2 + Keliling lingkaran kecil × 1/2 × 2
K = (2 × phi × r × 1/2) + (2 × phi × d) × 1/2 × 2
K = (2 × 1/2 × 3,14 × 10) + (2 × 3,14 × 10)
K = 31,4 + 31,4
K = 62,8 cm