Three prisms of crown glass, each have angle of prism `9^(@)` and two prisms of flint glass are used to make direct vision spectroscope. What will be the angle of flint glass prisms if `mu` for flint is `1.69` and `mu` for crown glass is `1.53` ?
A. `11.9^(@)`
B. `16.0^(@)`
C. `15.3^(@)`
D. `9.11^(@)`