Bill Has Worked for White Drywall for 4 Years

Bill has worked for White Drywall for 4 years.During this period White Drywall has contributed $25,000 to his retirement plan.Assuming the company uses graded vesting,how much will Bill be able to roll into an IRA if he left White Drywall at the end of 3 years?

A) $ 0
B) $ 5,000
C) $10,000
D) $15,000
E) $20,000