https://preparationpoint.info/mathematics-mcqs/c-takes-6-days-to-complete-half-of-a-work-and-d-takes-5-days-to-complete-1-3rd-of-the-same-work-they-take-turns-to-complete-the-task-if-c-works-for-the-first-4-days-in-how-many-days-will-d-complete/