Martin gifted his house, which is valued at $$600,000,$ to Trinity. However, Martin also gave Casey the right to live in the house for the rest of her life.

Which of the following is true:

a$.$ Casey will have to pay rent, otherwise she is making a monthly gift to Trinity.

b$.$ When Casey dies her estate will include the present value of her life estate, calculated based on her age.

c$.$ The value of Martin$$s gift to Trinity is $$600,000$ minus the annual exclusion.

d$.$ Casey$$s estate will not include the value of the life estate.