Gym membership operators offer customers a choice of tariffs, with the tariff broken into two parts: (a) a fixed monthly membership fee regardless of use, and (b) a charge per visit to the gym. The table below shows the tariffs offered by five companies; all figures are given in £. I am considering taking a membership with one of these and estimate that I will visit 12 times each month. Which company should I use to receive the lowest monthly bill?