A Manufacturer of a Certain Commodity Has Estimated That Her

A manufacturer of a certain commodity has estimated that her profit in thousands of dollars is given by the expression where x (in thousands) is the number of units produced. What production range will enable the manufacturer to realize a profit of at least $18,000 on the commodity?

A) Between 4,000 and 9,000 units.
B) Between 4,000 and 6,000 units.
C) Between 1,000 and 6,000 units.
D) Between 1,000 and 8,000 units.
E) Between 1,000 and 9,000 units.