I am guessing that the formula should include the purchase price, in which case my current result is 536/90 = 5.95 but that includes the undersuit that came with it.
Based on running costs its 71/90 = 79 pence.
So, any YD'ers out there seen reference to the forumla I am on about ? Or does anyone have a good way of reckoning how well your suit is performing ?
(apart from if its dry then its a good suit, which is stating the obvious
)