Light with frequency $6.7 \\times 10^{14}\\,\\text{Hz}$ travelling through vacuum is incident perpendicularly on a diffraction grating containing $4.0 \\times 10^5$ lines $\\text{m}^{-1}$. What is the angle between the neighbouring second-order and third-order intensity maxima?
- A$12^\circ$
- B$21^\circ$
- C$33^\circ$
- D$54^\circ$