An achromatic prism is made by combining two prisms ${\mathrm{P}}_1\left({\mathrm{\mu }}_{\mathrm{v}}=1.523,{\mathrm{\mu }}_{\mathrm{r}}=1.515\right)$ and ${\mathrm{P}}_2\left({\mathrm{\mu }}_{\mathrm{v}}=1.666,{\mathrm{\mu }}_{\mathrm{r}}=1.650\right)$ where $\mathrm{\mu }$ represents the refractive index. If the angle of the prism P1 is 10°,  then the angle of the prism P2 will be

• A

   5°

• B

  7.8°

• C

  10.6°

• D

  20°