Daniel bought a desktop computer and a laptop computer. Before finance charges, the laptop cost US$300 more than the desktop. He paid for the computers using two different financing plans. For the desktop the interest rate was 9% per year, and for the laptop it was 7% per year. The total finance charges for one year were US$365. How much did each computer cost before finance charges?

Let's denote the cost of the desktop computer as $D$ and the cost of the laptop computer as $L$.

According to the problem, the laptop cost $300 more than the desktop: $L = D + 300$

The interest rate for the desktop is 9% per year, and for the laptop, it is 7% per year. The total finance charges for one year were $365. Therefore, we can write the equation for the total finance charges as: $0.09D + 0.07L = 365$

Now, we substitute the expression for $L$ from the first equation into the second equation: $0.09D + 0.07(D + 300) = 365$

Next, we distribute the 0.07: $0.09D + 0.07D + 21 = 365$

Combine the terms involving $D$: $0.16D + 21 = 365$

Subtract 21 from both sides to isolate the term with $D$: $0.16D = 344$

Now, divide both sides by 0.16 to solve for $D$: $D = \frac{344}{0.16}$ $D = 2150$

So, the cost of the desktop computer is $2150. To find the cost of the laptop computer, we use the first equation: $L = D + 300$ $L = 2150 + 300$ $L = 2450$

Therefore, the cost of the desktop computer is $2150, and the cost of the laptop computer is$2450.