There are 45 pounds and 30 pounds of each type respectively.
Step-by-step explanation:
Since we have given that
Cost of first type = $2 per pound
Cost of second type = $7 per pound
Cost of mixture = $4 per pound
So, we need to find the quantity of each type to make 75 pounds of a blend.
We will use "Mixture and Allegations":
 First type     Second type
    2             7
           4
---------------------------------------------------
   7  - 4    :        4 - 2
   3       :         2
So, Quantity of first type would be
[tex]\dfrac{3}{5}\times 75=3\times 15=45\ pounds[/tex]
Quantity of second type would be
[tex]\dfrac{2}{5}\times 75=2\times 15=30\ pounds[/tex]
Hence, there are 45 pounds and 30 pounds of each type respectively.