$3.$ Setup and solve using Excel$$s solver. $($submit the Excel file with solver setup and entries$)$

Min: $3$Xa $+8$Xb $+6\mathrm{.}5$Xc $+8$Xd

St: $4$Xb $+6\mathrm{.}5$Xc $<=400+0\mathrm{.}25($Xa$+$Xb$+$Xc$)$

$2\mathrm{.}9$ Xa $+4$Xd $>=5505$Xb

Xb $>=4$XA $+5$Xc

Xc $>=12$

Xa$,$ Xb$,$ Xc$,$ Xd $>=0$