What is the Net Present Value of going back to school, considering the following scenario:

Claire is 50 years old and is considering going back to school. Without a college degree, she will make $10/hour. With a college degree, she will make $14/hour. She can get a free ride to college (no tuition or other expenses) and college takes 4 years to complete during which time she can't work. She plans to retire at 65. The discount rate is 5%.
a) -$38,176
b) $23,951
c) -$19,088
d) $21,519