Φ = MMF / S = 1600 / 5969 = 0.268 Wb
The MMF is given by:
MMF = NI = 100 x 5 = 500 A-turns
Φ = MMF / S = 500 / 3980 = 0.1256 Wb
S = l / (μ₀ * μr * A)