time (s)	concentration (mol/dm3)
0	0
20	4.5
40	11.3
60	16.2
100	25.8
140	37.1
200	51.3

a) Plot the data.

b) Fit a regression line to the data and give the estimated model.

c) What are the limits within which the true intercept can be found at 95% confidence level?

d) Check the assumption that the variance of the measurement error is the same at any time point (homoscedasticity)!