Please answer this question based on the following data.

The following information was obtained from matched samples.

The daily production rates for a sample of workers before and after a training program are shown below.

$\backslash$table$[[$Worker$,$Before,After$],[1,20,22],[2,25,23],[3,27,27],[4,23,20],[5,22,25],[6,20,19],[7,17,18]]$

The point estimate for the difference between the means of the two populations is

$-1$

$-2$

$0$

$1$