Interpret the circuit condition

Since the slider is being pulled, the resistance $R$ changes with time, so the current $I$ also changes with time.

For a circuit containing a cell of emf $E$, resistance $R$, and inductance $L$, the loop equation is $E = IR + L\frac{dI}{dt}$

Use the given rate of change of current

We are given: $\frac{dI}{dt} = 8\ \text{A/s}$ and at the instant considered, $R = 12\ \Omega$

Read the circuit values

From the circuit, the source emf is $48\ \text{V}$ and the inductance is $L = 1.5\ \text{H}$

Substitute into the circuit equation

$48 = 12I + 1.5 \times 8$

$48 = 12I + 12$

$12I = 36$

$I = 3\ \text{A}$

Final answer

$\boxed{3}$

Comparison with stored answer

Stored correct answer = $3$

Our derived answer also equals $3$, so they agree.