Researchers want to study noise levels produced by vehicles on a busy street. The mean noise level for 27 vehicles was 83.5 decibels, with a standard deviation is 2.7 decibels.

a) Find the critical Value for the 95% confidence interval. [2 marks] Write exact value from the table.

b) Find the 95% confidence interval of the true mean. [2 marks]

Round answers to two decimal places and separate your answers with commas. For example: (10.13,12.64).