Answer:
5,11 pounds of Costa Rican coffee and 64,89 pounds of Kenya coffee
Explanation:
First, we need to know the proportion of every coffee in the mix trying with different percentages until getting the result of $13,49  
  
($9,50*25%)+($13,80*75%)=$12,73  
  
($9,50*10%)+($13,80*90%)=$13,37  
  
($9,50*7,5%)+($13,80*92,5%)=$13,48  
  
($9,50*7,3%)+($13,80*92,7%)=$13,49  
  
So, the percentage of Costa Rican coffee is 7,3% and Kenya coffee is 92,7%  
And we can get the pounds required to get 70 pounds  
  
70*7,3%=5,11
  
70*92,7%=64,89
    
We need 5,11 pounds of Costa Rican coffee and 64,89 pounds of Kenyan coffee to create 70 pounds of mixed coffee that can sell for $13,49 per pound