Problem Solving (PS) | New homeowners Jo and Colin are painting their basement. Working alone

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