If \( m \) is the slope of a common tangent to the curves \( \dfrac{x^{2}}{16} + \dfrac{y^{2}}{9} = 1 \) and \( x^{2} + y^{2} = 12 \), then \( 12 m^{2} \) is equal to:
\( 6 \)
\( 9 \)
\( 10 \)
\( 12 \)