If the points of intersection of the ellipse \( \dfrac{x^2}{16} + \dfrac{y^2}{b^2} = 1 \) and the circle \( x^2 + y^2 = 4b,\, b>4 \) lie on the curve \( y^2 = 3x^2 \), then \( b \) is equal to:
\( 10 \)
\( 5 \)
\( 6 \)
\( 12 \)