You Need 50 Pounds of Two Commodities Costing $1 $y = 1.80 x + 2.40 ( 50 - x )$

You need 50 pounds of two commodities costing $1.80 and $2.40 per pound. Find the inverse function of the cost function $y = 1.80 x + 2.40 ( 50 - x )$ .

A) $y = \frac { 5 } { 3 } ( 240 - x )$
B) $y = \frac { 10 } { 3 } ( - 120 + x )$
C) $y = \frac { 5 } { 3 } ( - 240 - x )$
D) $y = \frac { 5 } { 3 } ( 120 - x )$
E) $y = \frac { 10 } { 3 } ( 120 + x )$