A farm used two harvesting machines, H and K, to harvest 100 acres of wheat. Harvesting machine H, working alone at its constant rate, harvested 50 acres of wheat in 8 hours. Then harvesting machine K was brought in, and harvesting machines H and K, working together at their respective constant rates, harvested the remaining acres of wheat in 5 hours. Harvesting machine K harvested how many acres of wheat per hour?  Select.
A) 7 B) 5 C) 12 D) 13 E) 15
Rate of H = 5 acres/hr   Remaining land to be harvested = 100 - 50= 
<gadget id="calculator">100 - 50</gadget>
<output>50</output>
50   Rate of H and K= 50/5= 
<gadget id="calculator">50/5</gadget>
<output>10</output>
10 acres/hr   Rate of K= 10 - 5= 
<gadget id="calculator">10 - 5</gadget>
<output>5</output>
5   Answer: 5
<result>B</result>
A farm used two harvesting machines, H and K, to harvest 100 acres of wheat. Harvesting machine H, working alone at its constant rate, harvested 50 acres of wheat in 8 hours. Then harvesting machine K was brought in, and harvesting machines H and K, working together at their respective constant rates, harvested the remaining acres of wheat in 5 hours. Harvesting machine K harvested how many acres of wheat per hour?