Answer: c 12 pounds of the $5.50-per-pound coffee, 8 pounds of the $9.20-per-pound coffee
Explanation:
Let x = Number of pound of first king.
y= Number of pound of second kind.
As per given , we have

substitute value of y from (i) in (ii), we get

Put this in (i), we get y= 20-8 = 12
Hence, he should blend 12 pounds of the $5.50-per-pound coffee, 8 pounds of the $9.20-per-pound coffee.
So the correct option is c.