First-grade tobacco costs $30 per kilogram while second-grade tobacco costs $20 per kilogram. If a blend contains only first and second grade tobacco, what must be the percentage of second-grade tobacco so that the blend would cost $22 per kilogram?
Choices:  A) 20%  B) 30%  C) 60%  D) 75%  E) 80%
Let x denote the share of the second-grade tobacco in the blend. Then the cost of a kilogram of the blend would go down as x∗20+(1−x)30=22 from where x=0.8 or 80%.   Answer: 80%
<result>E</result>
First-grade tobacco costs $30 per kilogram while second-grade tobacco costs $20 per kilogram. If a blend contains only first and second grade tobacco, what must be the percentage of second-grade tobacco so that the blend would cost $22 per kilogram?