Mike Gave His 25 Year Old Son $13,000 Worth of Stock

Mike gave his 25 year old son $13,000 worth of stock in 2009.When Mike died in 2010,that stock was worth $15,000.How much of that gift would potentially be subject to the federal gift and estate tax?

A) $30,000
B) $15,000
C) $13,000
D) $ 2,000
E) $ 0