The correct option (d) 13.5
Explanation:

2ℓ = 10 cm = 10–1 m
r = 15 cm = 15 × 10–2 m
OP = d = √(152 – 52) = 10√2 cm = √(200) cm
From tangent law,
BH = (μ0/4π)[{(2ℓ)(m)}/(OP2 + AO2)3/2]
∴ 0.4 ×10–4 = [(4π × 10–7 × 10–1 × m)/{4π [(200 + 25) × 10–4]3/2}]
∴ 0.4 × 104 = [m/(15 × 10–2)3]
Hence
m = 13.5 A.m.