Monthly Water Bills Dec Apr May June July Aug Sept Oct Nov Jan Feb Mar $ 46 $ 44 S44 $ 40 $ 42 $ 40 $ 38 S48 $ 50 $ 58 s62 $ 56 6. Write the formula for the mean water bill for the entire year using sigma notation and determine that mean. Round your answer to the nearest cent 7. Write the formula for the mean water bill for the first 6 months of the see using sigma notation and determine that mean. Round your answer to the 8. Write the formula for the mean water bill from April through November using sigma notation and determine that mean. Round your answer to the nearest nearest cent. cent. 9. Write the sigma notation mean formula for the consecutive 3-month period that would have the highest mean of the year. Use the following table to answer questions 10-12. Elizabeth wants to change cell phone plans. Before contacting the service provider, she makes a table of her cell phone minutes used over the course of a week.