In Exercise 2.10 we examined the data shown in Appendix D, Table D.4. that shows winning speeds at the Indianapolis 500 for the years 1911 - 1971, excluding the war years 1917-1918 and 1942-1945. It is conjectured that technology changes during the wars may have introduced discontinuities into the relation between time and speed. To examine this, fit a model with three linear segments having join points at 1917.5 and 1943.5.