Fertilizer. A farmer wants to use two brands of fertilizer for his soybean crop. Brand A contains 18% nitrogen, 24% phosphate, and 12% potash. Brand B contains 5% nitrogen, 10% phosphate, and 15%...

Fertilizer.
A farmer wants to use two brands of fertilizer for his soybean crop. Brand A contains 18% nitrogen, 24% phosphate, and 12% potash. Brand B contains 5% nitrogen, 10% phosphate, and 15% potash.

(Source: Spectrum Analytic, Inc.)

(A) How many pounds of each brand of fertilizer should he add to each acre if he wants to add at least 50 pounds of phosphate to each acre?

(B) How many pounds of each brand of fertilizer should he add to each acre if he wants to add at most 60 pounds of potash to each acre?