The domestic demand $(UpperQ$ Subscript $DD)$ for wheat $in$ the United States $is$ estimated $tobe$

Upper $Q$ Subscript DDequals$1430$minus $55P,$

where the quantity $of$ wheat $is$ measured $in$ millions $of$ bushels per year. Suppose China also demands $U.S.$ wheat $(UpperQ$ Subscript $DC)$ and that its demand $is$ given $by$

Upper $Q$ Subscript DCequals$1800$minus$90P.$

Part $2$

What $is$ the total demand for $U.S.$ wheat, assuming the only two sources $of$ demand are domestic and Chinese?

Part $3$

The total demand for $U.S.$ wheat $is$

Part $4$

$A.$

Upper $Q$ Subscript Upper Dequals$1430$ minus $55$ Upper $P$ for all $P.$

$B.$

Upper $Q$ Subscript Upper Dequals$3230$minus$145P$ for all $P.$

$C.$

Upper $Q$ Subscript Upper Dequals$3230$minus$145P$ for Pless than $or$ equals $$26$ and Upper $Q$ Subscript Upper Dequals$1800$ minus $90$ Upper $P$ for Pgreater than $$26.$

$D.$

Upper $Q$ Subscript Upper Dequals$3230$minus$145P$ for Pless than $or$ equals $$20$ and Upper $Q$ Subscript Upper Dequals$1430$ minus $55$ Upper $P$ for Pgreater than $$20.$

$E.$

Upper $Q$ Subscript Upper Dequals$3230$minus$145P$ for Pless than $or$ equals $$20$ and Upper $Q$ Subscript Upper Dequals$1800$ minus $90$ Upper $P$ for Pgreater than $$20.$