This shifts the star’s spectral lines toward the blue end of the spectrum. If the star is moving away from us, it’s waves are effectively stretched out when they reach earth, increasing their wavelength. This shifts the star’s spectral lines toward the red end of the spectrum.
The concept that we need here to give a proper solution is mutual inductance.
The mutual inductance is given by the expression

Where,
I = current
N = Number of turns
Flux through the solenoid.
Part A) Then we have in our values that,



Replacing in the equation,


Part B) Here is required the Flux, then using the same expression we have that

We conserve the same value for the Inductance but now we have a current of 2.6, then


Therefore the flux in Solenoid 1 is 
I think wavelength is the correct answer. Correct me if Im wrong. Hope this helps!