$($a$)$ Pricing Communications Nodes: Build a regression model to predict the cost of installing a communication node $($COST$)$ from the number of access ports $($NUMPORTS$),$ bandwidth $($BANDWIDTH$),$ and portspeed $($PORTSPEED$).$ The COST is measured in U$.$S$.$ dollars. The data are in the worksheet named COMNODE,HW$7.$

State the model equation.

$=1$NUMPORTS $+2$BANDWIDTH $+3$COST$=0+1$NUMPORTS $+2$BANDWIDTH $+3$COST$=1$NUMPORTS $+2$BANDWIDTH $+3$PORTSPEED$=0+1$NUMPORTS$=0+1$NUMPORTS $+2$BANDWIDTH $+3$PORTSPEED$=0+1$COST $+2$BANDWIDTH $+3$PORTSPEED