By will, D left Blackacre to A for life, remainder to B. Ds residuary estate was left to S, Ds spouse Both A and B effectively, under IRC section 2518 disclaimed their interests in Blackacre.

a. How may this affect the martial deduction for Ds estate?

b. Is the answer the same if C is the residuary legatee under Ds will, but after Ds death. A and B effectively direct the transfer of Blackacre to S?

c. Under what circumstances (and with what effect) might a surviving spouse be likely to disclaim an interest in property left to the surviving spouse?