New homeowners Jo and Colin are painting their basement. Working alone, Jo could paint the entire basement in seven hours; working alone, Colin could paint it in six. They work together at their separate and constant rates for two hours; then Colin goes to work at his office while Jo continues to paint. How long in hours and minutes will it take for the basement to be completely painted?

A. 3:00
B. 3:30
C. 4:00
D. 4:18
E. 4:40

Answer: E

Source: Veritas Prep