The correct equation for a Master Budget Variance is

$($Budgeted volume $$ Budgeted price$)+($Actual volume $$ Actual price$).$

$($Budgeted volume $$ Actual price$)+($Actual volume $$ Budgeted price$).$

$($Budgeted volume $$ Actual price$)-($Actual volume $$ Budgeted price$).$

$($Actual volume $$ Actual price$)-($Budgeted volume $$ Budgeted price$).$