A thin prism having refracting angle $$10^\circ$$ is made of glass of refractive index 1.42. This prism is combined with another thin prism of glass of refractive index 1.7. This combination produces dispersion without deviation. The refracting angle of second prism should be

A

$$8^\circ$$

B

$$10^\circ$$

C

$$4^\circ$$

D

$$6^\circ$$