National Scan, Inc., sells ratio frequency inventory tags. Monthly sales for a 6-month period were as follows:

Month:	Sales
Feb	65
Mar	66
Apr	66
May	71
Jun	72
Jul	72

Disregard the demand pattern of the given time series, You are asked to use the time series to derive a trend equation. In order to derive the trend equation is F_t = a + bt, you have to compute several components to compute the values for the variables a and b. Answer the following questions pertaining to information that are relevant to deriving the trend equation.

a) The Σty =

b) The Σy =