1. **State the problem:** Find the mean (average) of the given data set. The median is already given as 77.00. 2. **Formula for mean:** $$\text{mean} = \frac{\text{sum of all data values}}{\text{number of data values}}$$ 3. **Count the number of data values:** There are 70 values in total. 4. **Sum all data values:** $$55.9 + 64.4 + 69.7 + 73.7 + 78.5 + 82.4 + 89 + 90.3 + 67.7 + 62.6 + 80.9 + 68.5 + 83 + 74.2 + 81.2 + 83.3 + 90 + 78.1 + 77.2 + 78.3 + 81.7 + 70.3 + 68 + 79.9 + 75.6 + 76.6 + 63.2 + 78.5 + 64.3 + 72.8 + 75.8 + 80.9 + 65.2 + 76.4 + 78.5 + 78.5 + 82 + 68.5 + 81.5 + 76.4 + 78.1 + 72.3 + 83.3 + 71.3 + 93.6 + 80.1 + 71.9 + 80.7 + 72.1 + 71.7 + 82.6 + 82.3 + 82.3 + 81.5 + 82.6 + 86.8 + 73 + 77.7 + 72.6 + 62.6 + 83.3 + 71.3 + 69.3 + 65.6 + 82 + 83.3 + 76.8 + 76.8 + 71 + 70.3 = 5443.3$$ 5. **Calculate the mean:** $$\text{mean} = \frac{5443.3}{70}$$ 6. **Simplify:** $$\text{mean} = 77.76$$ 7. **Final answer:** The mean of the data set is **77.76** rounded to two decimal places. The median is given as 77.00, which is correct.