16Meaning of mass coefficient

16  Meaning of mass coefficient  (1) In this section, for a relevant operation in which natural gas is measured by mass: base year means:  (a) if an election has been made in relation to the operation under section 54—the 2012‑13 year of tax; or  (b) otherwise—the year of tax in which the actual mass of project natural gas first exceeds the estimated average annual mass of project natural gas for the operation. Note: If the estimated average annual mass of project natural gas changes from one year of tax to another, the base year for the calculation of the mass coefficient may also change.  (2) The mass coefficient for a relevant operation in which natural gas is measured by mass in a year of tax (the current year) is:  MA means the actual mass of project natural gas for the current year. MB means:  (a) if the current year is before the base year—the estimated average annual mass of project natural gas; or  (b) if the current year is the base year—MA; or  (c) if the current year is after the base year—the amount worked out using the formula:      Mn means the actual mass of project natural gas for year n.   n means a year of tax, with the base year being year 1, the year after the base year being year 2, and so on.   N means the number of years of tax from the base year to the current year (inclusive).