Answer:
D) 80%
Explanation:
IRS Section 267(c)(4) establishes that the sister will be considered as constructive owner of the stock that her family owns. Family is defined as brothers (25%), sisters, spouse, ancestors (father 40% and mother 15%), children, and grandchildren.
In this case, Farber's sister would constructively own 25% + 40% + 15% = 80% of the bank's stocks.