15: Coats of paint [***]

Wes Carroll's Puzzler

Working alone, I put two coats of paint on a wall, one before lunch and one after. Yesterday, I began at the usual time. Two hours before lunch I was joined by my good friend Aidan, who paints at the rate of 600 sqft per workday, and who left just as the first coat was finished. I promptly began the second coat, and had lunch at the usual time. One hour before quitting time, I had painted a second coat everywhere except where Aidan had painted that morning. If we each have the same workday, and if each of us works at a constant rate (albeit not necessarily the same rate as the other), what was the area of the wall? // Spiciness: *** out of ****