Electromagnetic Induction

In the circuit shown, when the current '$i$' is $3\text{A}$ and increasing at the rate of $1\text{A/s}$ the measurement of the potential difference between A and B is $12\ \text{V}$. But when the same current $3\text{A}$ is decreasing at the rate of $1\text{A/s}$, the measured potential difference $V_{AB}$ between A and B is $6\text{V}$. The value of 'R' in the circuit is