A spectrograph's trihedral prism is manufactured from glass whose refractive index varies with wavelength as n = A + B/2, where A and B are

A spectrograph's trihedral prism is manufactured from glass whose refractive index varies with wavelength as n = A + B/λ2, where A and B are constants, with B being equal to 0.010μm 2. Making use of the formula from the foregoing problem, find:
(a) How the resolving power of the prism depends on λ; calculate the value of λ/δλ in the vicinity of λ1 = 434 nm and λ2 = 656 nm if the width of the prism's base is b = 5.0 cm;
(b) The width of the prism's base capable of resolving the yellow doublet of sodium (589.0 and 589.6 nm).