Rafael's Coffee Shop makes a blend that is a mixture of two types of coffee. Type A coffee costs Rafael $5.70 per pound, and type B coffee costs $4.25 per pound. This month, Rafael made 139 pounds of the blend for a total cost of $706.75. How many pounds of type B coffee did he use?

A. 45 pounds
B. 50 pounds
C. 55 pounds
D. 60 pounds

Let's denote the pounds of type A coffee as A and the pounds of type B coffee as B. The problem states that Rafael made 139 pounds of the blend, so [tex]$A + B = 139$[/tex].

The cost of type A coffee is $5.70 per pound, and the cost of type B coffee is $4.25 per pound. The total cost is $706.75, and we can express this in terms of the weights and costs:

[tex]\[5.70A + 4.25B = 706.75\][/tex]

Now, we have a system of two equations:

[tex]\[ \begin{cases} A + B = 139 \\ 5.70A + 4.25B = 706.75 \end{cases} \][/tex]

Solving this system, we find that A = 89 and B = 50. Therefore, Rafael used 50 pounds of type B coffee.

This can be confirmed by substituting these values back into the total cost equation:

[tex]\[5.70 \times 89 + 4.25 \times 50 = 706.75\][/tex]

Hence, the final answer is that Rafael used 50 pounds of type B coffee.