30. Parking. Hoping to lure more shoppers downtown, a city builds a new public garage in the central business district. The city plans to pay for the structure through parking fees. During a two-month period (44 weekdays), daily fees collected averaged $126, with a standard deviation of $15.

a) What assumption must you make in order to use these statistics for inference?

b) Write 90% confidence interval for the mean daily income this parking garage will generate.

c) Interpret this confidence interval in context.

d) Explain what "90% confidence" means in this context.

e) The consultant who advised the city on this project predicted that parkin revenues would average $130 per day. Based on your confidence interval, do you think the consultant was correct? Why?