Problem:
Mr. and Mrs. X plan to file a joint return for 2013. Neither is over 65 or blind, nor do they have any dependents.
Required:
Question 1: What is the amount of gross income required before they must file a return?
A. $12,200
B. $13,900
C. $16,100
D. $20,000
Note: Please describe comprehensively and provide step by step solution.