(6) Grantor creates a trust with income to
x
or
x
's estate for Grantor's life, and a remainder to
Y
or
Y
's estate. Grantor predeceases
x
and
Y
(and Z, where
Z
appears in the subparts below). How, if at all, does Section 2036 apply in the following situations? (a) Grantor, as trustee, retains a power to invade corpus for Z. ' (b) Grantor, as trustee, retains a power to accumulate income and add it to corpus. . (c) Grantor, as trustee, retains a power to invade the corpus of the trust for
x
. .