A new housing development will have 105 houses. All the houses have the same floor plan and dimensions. Carlos can paint a house by himself in four days. Manuel can paint a house in 3 days. A normal workweek is 5 days. How many work weeks would it take them to work together to paint 105 houses? Now supposed that they need to finish in 28 weeks but only have enough to ph for one extra crew member. What is the greatest number of days the third worker can take to paint each house?