$(S$&$W10\mathrm{.}5)$ Consider the model with a single regressor. This model also can $be$

written $as$

$Y_{it}={}_0+{}_1{x}_{1,it}+{}_{2}B{2}_t+$cdots$+{}_{T}B{T}_t+{}_{2}D{2}_i+$cdots$+{}_{n}D{n}_i+u_{it},$

where $B{2}_t=1ift=2$ and $0$ otherwise, and $D{2}_i=1ifi=2$ and $0$ otherwise,

and $so$ forth. How are the coefficients $({}_0,{}_2,$dots,${}_T,{}_2,$dots,${}_n)$ related $to$ the

coefficients $({}_1,$dots,${}_n,{}_1,$dots,${}_T)?$