Light of wavelength $\lambda$ is incident normally on a diffraction grating that has a slit separation of $\frac{7\lambda}{2}$. What is the greatest number of maxima that can be observed using this arrangement?

Light of wavelength $\lambda$ is incident normally on a diffraction grating that has a slit separation of $\frac{7\lambda}{2}$. What is the greatest number of maxima that can be observed using this arrangement?