In 2015, Jessica placed $250,000 in a savings account listing ownership as follows: Jessica, Keri, and Jason,

Question:

In 2015, Jessica placed $250,000 in a savings account listing ownership as follows: "Jessica, Keri, and Jason, joint tenancy with the right of survivorship." Keri and Jason are Jessica's adult children. In 2016, Jason withdrew $50,000 from the account. In 2018, when the account had a balance of $210,000, Jessica predeceases her children.
What are the transfer tax consequences of these transactions in:
a. 2015?
b. 2016?
c. 2018?