Long description

A five-figure summary. The diagram forms three sides of a rectangle, with the bottom line missing. It therefore has a vertical line to the left, a horizontal line across the top and a vertical line to the right. To the left of the left vertical line is written n = 20. Towards the bottom of the left vertical line and to its right is written 90 and above that 130. Beneath the middle of the horizontal line is written 150. To the left of the second vertical line and level with 130 is written 180. Below that and level with 90 is written 270.