Given the following forecasting data, using trend projection, the slope of the prediction line is is

$\backslash$table$[[$Month$,$Period,$\backslash$table$[[$Demand $($in$],[$Thousands$)]]],[$April$,1,19],[$May$,2,20],[$June$,3,18],[$July$,4,19],[$August$,5,17]]$

$10$

$-5$

$-\mathrm{.}5$

$20\mathrm{.}1$