Kevin purchased a house 20 years ago for $100,000 and he has always lived in the house. Three years ago Kevin married Karen, and she has lived in the house since their marriage. If they sell Kevin’s house in December 2019 for $425,000, what is their taxable gain on a joint tax return? 

a. $0 

b. $75,000 

c. $125,000 

d. $250,000