When A and B collaborate only with C, the number of days they would take to complete a project, working together, would be 12.5% more than what they would take when they collaborate only with D who is twice as efficient as C. If A and B decided to collaborate with both C and D, then the number of days they would take to complete the project will be what percentage less than the number of days they would have taken to complete it had they collaborated only with C?