In 2014,Father Sold Land to Son for $50,000 Cash and an Installment

In 2014,Father sold land to Son for $50,000 cash and an installment note for $150,000 due in 2018.Father's basis was $100,000.In 2015,after paying $8,000 interest but nothing on the principal,Son sold the land for $300,000 cash.What gain,if any,must Father recognize in 2015?

A) $0
B) $75,000
C) $100,000
D) $200,000
E) None of these