An interference is observed due to two coherent sources $\mathrm{A}$ and $\mathrm{B}$ separated by a distance $4\mathrm{\lambda }$ along Y-axis where $\mathrm{\lambda }$ is the wavelength of the light source used. A detector $\mathrm{D}$ is moved along the positive X-axis. Find the total number of maxima points are observed on the X-axis excluding the points $\mathrm{x}=0$ and $\mathrm{x}=\mathrm{\infty }$?

Hence, the correct answer is 3.