If you are using the method of least squares for fitting trends in an annual time series containing 25 consecutive yearly values,

(a) what coded value do you assign to X for the first year in the series?
(b) what coded value do you assign to X for the fifth year in the series?
(c) what coded value do you assign to X for the most recent recorded year in the series?
(d) what coded value do you assign to X if you want to project the trend and make a forecast five years beyond the last observed value?