When sodium yellow light (λ = 589 nm) is used in a double-sl…

When sodium yellow light (λ = 589 nm) is used in a double-slit experiment, the first-order maximum (bright spot) is 0.035cm from the central maximum. When another source of unknown wavelength is used on the same slit and screen setup, the first-order maximum occurs at 0.032 cm from the center.  What is the unknown wavelength in nm? *Hint: use the small angle approximation,