ail bought a desktop computer and a laptop computer. Before finance charges, the laptop cost US$250 less than the desktop. She 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 6% per year. The total finance charges for one year were US$300. 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 $250 less than the desktop: $L = D - 250$

The interest rate for the desktop is 9% per year, and for the laptop, it is 6% per year. The total finance charges for one year were $300. Therefore, we can write the equation for the total finance charges as: $0.09D + 0.06L = 300$

Now, substitute the expression for $L$ from the first equation into the second equation: $0.09D + 0.06(D - 250) = 300$

Distribute the 0.06: $0.09D + 0.06D - 15 = 300$

Combine like terms: $0.15D - 15 = 300$

Add 15 to both sides of the equation: $0.15D = 315$

Divide both sides by 0.15: $D = 2100$

Now, substitute $D = 2100$ back into the equation $L = D - 250$: $L = 2100 - 250$ $L = 1850$

Therefore, the cost of the desktop computer before finance charges is $2100, and the cost of the laptop computer before finance charges is$1850.

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 $250 less than the desktop: $L = D - 250$

The interest rate for the desktop is 9% per year, and for the laptop, it is 6% per year. The total finance charges for one year were $300. Therefore, we can write the following equation for the total finance charges: $0.09D + 0.06L = 300$

Now, substitute $L$ from the first equation into the second equation: $0.09D + 0.06(D - 250) = 300$

Simplify the equation: $0.09D + 0.06D - 15 = 300$ $0.15D - 15 = 300$

Add 15 to both sides of the equation: $0.15D = 315$

Divide both sides by 0.15: $D = \frac{315}{0.15}$ $D = 2100$

Now, substitute $D$ back into the first equation to find $L$: $L = 2100 - 250$ $L = 1850$

Therefore, the cost of the desktop computer before finance charges was $2100, and the cost of the laptop computer before finance charges was$1850.