which of the following statements is a correct computation of interest for the look-back method?

a) interest is computed by recalculating the original tax liability using the section 6621 overpayment rate.

b) interest is computed on the difference in the original tax amount and the recomputed tax liability from the prior year's tax return.

c) interest is computed on the difference in the recomputed tax liability and the original tax amount using section 6621 overpayment rate.

d) interest is computed by recalculating the original tax liability using the prior year's tax return.