Several years ago, D created a trust under which the income was to be paid to D's sibling, S for S's life, then to D for D's life.

Several years ago, D created a trust under which the income was to be paid to D's sibling, S for S's life, then to D for D's life. Upon the death of the survivor of D and S, the corpus was to be distributed to R or R's estate. At D's death more than three years later, D was survived by S and R. The corpus of the trust was then worth $300k with S and R's interests worth $100k and 200k respectively. What amount should be included in D's gross estate?