Colston knows that his teacher loves drinking coffee and one day wants to see how much she drinks each week. He sees that she has a 20-ounce thermos and when she makes her coffee she pours a 1/2 cup of milk in, and then fills the coffee to the top. She does this twice a day. After the five-day school week, he decides to tell her, and when she hears how much coffee she drinks, she decides to drink 1/4 of what she normally drinks. How many ounces of coffee does she now drink a week?