A questionnaire that college economics students can use to investigate the degree and nature of competition in the retail market for petrol is provided. A simple computer program is included to help in the analysis of the questionnaire. (Author/RM)

A previous article examined the amount of fuel that could constantly burn each second and achieve a safe landing. This article investigates some ways to burn variable amounts of fuel according to some mathematical function (such as an arithmetic progression). Several assumptions (such as a massless fuel) are made. (JN)