Answer
$-0.000085 Amp/s$ or, $-8.5 \times 10^{-5}$
Work Step by Step
Given: $V=IR$
Chain rule : $\dfrac{dV}{dt}=V_I(\dfrac{dI}{ dt})+V_r(\dfrac{dR}{dt})$
This implies that
$\dfrac{dV}{dt}=R(\dfrac{dI}{ dt})+I(\dfrac{dR}{dt})$
Now, we have
$-(0.1)=(400) \cdot (\dfrac{dI}{ dt})+(0.08) \cdot (0.03)$
or, $-(0.1)=(0.00240)+(400) \cdot (\dfrac{dI}{ dt})$
This gives:
$\dfrac{dI}{dt}=-0.000085 Amp/s$
or, $\dfrac{dI}{dt}=-8.5 \times 10^{-5}$
