The cost of 7 pounds is 280 dollars.
Therefore the cost of per pound is by unitary method is,
![(280)/(7)=40\text{ }](https://img.qammunity.org/2023/formulas/mathematics/college/rooy7uusclu52ozyngwwbc1l8rfbg6oed9.png)
Therefore, the cost per pound is 40 dollar.
It is given that the pound are decrease by 25 percent.
Therefore.,
The cost per pound reduces to ,
![40*(25)/(100)=10.](https://img.qammunity.org/2023/formulas/mathematics/college/djxalkvpneqzmdq8m7dl3svmrnel9i58ao.png)
To calculate the cost per pound after decrease is,
The difference of original cost per pound and cost per pound after decrease.
![40-10=30.](https://img.qammunity.org/2023/formulas/mathematics/high-school/zgkixb93aoubvg6nyw1khd6rdx239u6wbw.png)
The cost per pound after decrease is 30 dollar.