Current $3$A flows through $200$ twins on the center log$.$ Core oross section area is ${10}^{-3}{m}^2.{}_r=5000$

a$)$ Find $\frac{?}{\text{b}\text{a}\text{r}}(B)$ in $(1)(2)(3)$ and airgap.

b$)$ Find I in $(1)(2)(3)$ and airgap.

c$)$ Find $\frac{?}{\text{b}\text{a}\text{r}}(H)$ in $(1)(2)(3)$ and airgap.