Statistics Questions

The variance ${\sigma }^2$ of a random variable $X$ is given by:

Which of the following is correct regarding the analysis of four components of time series analysis?

Using the base year 1985, the index number calculated by the simple aggregate method for four items (A, B, C, D) is $125$. Given:Prices in 1985: $75,85,\alpha ,100$ Prices in 1986: $90,115,75,\beta$ Find the value of $(4\beta -5\alpha )$.