Alice the artist and her two assistants each create art at constant, but different, rates. They always start at $8:00$ AM, and all three always take the same amount of time to eat lunch. On Monday the three of them completed $50\%$ of a large mural, quitting at $4:00$ PM. On Tuesday, when Alice wasn't there, the two assistants completed $20\%$ of the mural and quit at $2:30$ PM. On Wednesday Alice worked by herself and finished the mural by working until $5:30$ PM. How long, in minutes, was each day's lunch break?