For a joint$-$and$-$survivor annuity for two unmarried people purchased entirely with the funds of the survivor, how much is included in the gross estate of the first to die?

A$)50\%$ of the value of the surviver annuity

B$)0\%$

C$)100\%$ of the value of the survivor annuity

b$)$ It depends on the ages of the $2$ annuitants