Calc K-Shell X-Ray Series Wavelengths for Zirconium Atom

[freefallin38]

Calculate the three longest wavelengths and the series limit for the K-shell x-ray series of the zirconium atom.
(a) λ(Kα) = 79.8832 pm
(b) λ(Kβ) = 67.401142 pm
(c) λ(Kγ) = 63.90653 pm
(d) The series limit is _____ pm

So I have solved parts a-c. For part d, the series limit, I tried solving using the following formula:
1/lambda=Z^2*R(1/(nl)^2-1/(nu)^2), where nl=1, nu=infinity, Z=40 so it reduced to:
Lambda=1/(Z^2R)= 56.9543545pm, but this answer is wrong. Can anyone see where I'm going going wrong?

 

[dynamicsolo]

At a guess, I'd say you may have punched something into your calculator wrong for part (d). Isn't 3/4 of 79.88 more like 59.91 ?