For Dana, one of the most favourite things about being retired is that she can enjoy an afternoon nap. On any given day, the amount of time that Dana naps is uniformly distributed between 37.1 and 70.3 minutes. Assume that the amount of time Dana naps is independent from day to day. This week, Dana only took naps on Wednesday, Friday and Sunday. Calculate the variance of the total amount of time that Dana napped this week. Do not include any units in your answer.