Hyperbola

Let e1 and e2 be the eccentricities of the ellipse ‌

x2

b2

+‌

y2

25

=1 and the hyperbola ‌

x2

16

−‌

y2

b2

=1, respectively. If b<5 and e1e2=1, then the eccentricity of the ellipse having its axes along the coordinate axes and passing through all four foci (two of the ellipse and two of the hyperbola) is: