If I load the dataset below and execute the following code

collapse $($mean$)$ outcome, by$($treat$)$

Then the resulting dataset will have how many observations total?

$\backslash$table$[[,$treat,outcome,session$],[1,1,5\mathrm{.}995928,1],[2,1,8\mathrm{.}883919,2],[3,1,2\mathrm{.}842385,1],[4,1,9\mathrm{.}034828,2],[5,0,6\mathrm{.}260192,1],[6,0,4\mathrm{.}328012,2],[7,0,8\mathrm{.}655678,1],[8,0,4\mathrm{.}522437,2]]$