A prism of certain angle deviates the red and blue rays by 8o and 12o respectively. Another prism of the same angle deviates the red and blue rays by 10o and 14o respectively. The prisms are small angled and made of different materials. The dispersive powers of the materials of the prisms are in the ratio
5 : 6
9 : 11
6 : 5
11 : 9