If the foci of the ellipse $\large\frac{x^2}{25}+\frac{y^2}{16}=1$ and the hyperbola $\large\frac{x^2}{4}-\frac{y^2}{b^2}=1$ coincide, then $b^2=$

Question

$$(a)\;4 \quad (b)\;5 \quad (c)\;8 \quad (d)\;9$$