(a) Method: for parallel current-carrying wires, field due to a wire at distance $d$ is $B=\dfrac{\mu_0I}{2\pi d}$, and force per unit length between two parallel wires carrying currents $I_1$, $I_2$ separated by $d$ is $f=\dfrac{\mu_0I_1I_2}{2\pi d}$ (attractive for like/parallel currents, repulsive for unlike/antiparallel currents). Apply these formulas using the actual distances between the three conductors (carrying $2I$, $I$, $3I$) from the original figure, which were not fully legible in the extracted text, to find the net field and net force per unit length.

(b) Loop of sides $l$, $b$ (area $A=lb$), resistance $R$, in field $B=B_0\sin\omega t$:

(i) Flux: $\Phi=B_0\sin(\omega t)\times lb$

Induced emf: $$\varepsilon=-\frac{d\Phi}{dt}=-B_0lb\omega\cos(\omega t)$$

(magnitude, peak value $=B_0lb\omega$)

(ii) Peak current: $I_0=\dfrac{B_0lb\omega}{R}$

Effective (rms) current:

$$I_{rms}=\frac{I_0}{\sqrt2}=\frac{B_0lb\omega}{\sqrt2R}$$