Leena can go to her office in two ways also return to her home from the same route. The distance of the first route is 5 km while the distance of the second route is 7 km. For some reasons, she is unable to go to the office for two consecutive days by the same route. If she goes through the first route on Monday, then how many km does she cover the second route that week?

• A. 21 km
• B. 14 km
• C. 42 km
• D. 28 km