The microwave spectrum of 12C16O shows that the transition from J = 0 to J = 1

Question:

The microwave spectrum of 12C16O shows that the transition from J = 0 to J = 1 requires electromagnetic radiation with a wavelength of 2.60 × 10-3 m.
a. Calculate the bond length of CO. See Exercise 56 for the atomic mass of 16O.
b. Calculate the frequency of radiation absorbed in a rotational transition from the second to the third excited state of CO.