The Leaning Tower of Pisa no longer leans quite so much after a £20 million project to save it was hailed a complete success yesterday.

The Leaning Tower of Pisa has been straightened by 18 inches (45 centimetres), returning it to its position of 1838. It has been leaning since 1173.

The lean has been measured and documented over many years and the data are given in the Table below:

Year Lean in metres
1298 1.43
1360 1.63
1372 1.43
1550 3.79
1787 3.79
1812 3.79
1817 3.84
1911 4.04
1935 4.80
1997 5.20


Using appropriate plots and analysis produce a model of the movement in the tower over the years. You should:

State the model and interpret the model.
Discuss the significance of the parameters in the model.
Validate the model and any assumptions made by the model.
Estimate what the lean would have been in 2007 if corrective action had not been taken?