Week $1$: Convolution

Convolve the following kernel and image, and write your solution in the answer box:

Kernel $=$

$\backslash$table$[[1,1,1],[1,-8,1],[1,1,1]]$

Image $=$

$\backslash$table$[[0,0,0,0,0,0,0,0,0,0,0,0],[0,0,0,0,0,0,0,0,0,0,0,0],[0,0,0,0,0,0,0,0,0,0,0,0],[0,0,0,0,0,10,10,0,0,0,0,0],[0,0,0,0,10,10,10,10,0,0,0,0],[0,0,0,10,10,10,10,10,10,0,0,0],[0,0,0,10,10,10,10,10,10,0,0,0],[0,0,0,10,10,10,10,10,10,0,0,0],[0,0,0,10,10,10,10,10,10,0,0,0],[0,0,0,0,0,0,0,0,0,0,0,0],[0,0,0,0,0,0,0,0,0,0,0,0],[0,0,0,0,0,0,0,0,0,0,0,0]]$

$($a$)$ What does this kernel do$?$

$($b$)$ Why are the border tiles of the answer image blacked out?