Mahmed (age 19) is a student (and US taxpayer) who works part-time during school breaks. In 2016 he earned $4,000 from all of his jobs. His parents gave him $6,000 as a gift in 2016. Mahmed wants to start investing for his retirement after listening to some old bald guy talk about the importance of starting to invest for retirement as early in life as possible. What is the maximum that Mahmed can invest in his Roth IRA for tax year 2016?

A. $4,000
B. $5,500
C. $6,000
D. $13,000