The annual maintenance bills of similar buildings in down town Nairobi were related to their age with the following results.
First row age A. Age (yrs) and second row M. Maintenance bills (000 shs)

Age 15 5 25 40 5 20 10 30 445 15 25 35 10 30
M 39 24 115 105 50 86 67 90 140 112 70 186 43 126

a) fit a regression line to this data (5 marks)

b) find the 95 % confidence interval estimate of the maintenance cost of the building for
age in years, assuming the data is homoscedastic (5 marks)

c) Test the significance of the regression coefficients b and a at the .05 significance level (5 marks)