b
The expression to calculate the induced magnetic field is given as,

\(B =\mu_{0}( H + I )\)

\(=\mu_{0}\left(\frac{ N }{2 \pi r } \times i + I \right)\)

Substitute the values.

\(10=\mu_{0}\left(\frac{ N }{2 \pi r } \times i + I \right)\)

\(I=\frac{10}{4 \pi \times 10^{-7}}-\frac{400 \times 2 \times 2}{2 \pi \times 2.5}\)

\(=\frac{10^{8}}{4 \pi}\)