1. **State the problem:** We need to compute the mean (average) of the given day sales: 1203.00, 1203.21, 2013.99, 2103.12, and 1231.00. 2. **Formula for the mean:** The mean of $n$ numbers $x_1, x_2, ..., x_n$ is given by $$\text{Mean} = \frac{x_1 + x_2 + \cdots + x_n}{n}$$ 3. **Apply the formula:** Here, $n=5$ and the numbers are $1203.00, 1203.21, 2013.99, 2103.12, 1231.00$. 4. **Sum the numbers:** $$1203.00 + 1203.21 + 2013.99 + 2103.12 + 1231.00 = 8754.32$$ 5. **Calculate the mean:** $$\text{Mean} = \frac{8754.32}{5}$$ 6. **Simplify the division:** $$\text{Mean} = 1750.864$$ **Final answer:** The mean of the day sales is $1750.864$.