c
\(B _{\text {due to solenoid }}=\mu_0 nI\)

\(\Phi_{\text {through square }}=\mu_0 nI \times A \quad( A =\text { Area })\)

\(Emf =\mu_0 nA \times \frac{ dI }{ dt }\)

\(=\mu_0 n A \times I _0 \omega \cos \omega t\)

\(\text { Emf amplitude }=\mu_0 n A \times I _0 \omega\)

\(=4 \pi \times 10^{-7} \times \frac{50}{10^{-2}} \times 4 \times 10^{-4} \times 2.5 \times 700\)

\(=44 \times 10^{-4}\,V\)