Recall the general linear model given by

$Y=x+lon,$

where $Y=(Y_1,$dots,$Y_n{)}^{TT}$ is the vector of responses, $x$ is the $np$ design matrix, $=({}_0,$dots,${}_{p-1}{)}^{TT}$ is the parameter vector and $lon=(lo{n}_1,$dots,$lo{n}_n{)}^{TT}$ is the error vector.

Say that you have $145$ observations and you want to write the simple linear model

$y={}_0+{}_{1}x+lon$

in matrix form. How many rows does $x$ have? What is the value of the first element of $x($ie $($:$x_{(1,1)}\}?$