Answer:
a) $1,920
b) $9,920
Step-by-step explanation:
Step 1. Gather all of the information.
The amount borrowed will be the principal or starting amount P:
![P=8,000](https://img.qammunity.org/2023/formulas/mathematics/college/9pcfcns8wrcuyxshpfxx3kfr89r7qkrevo.png)
The interest rate will be r:
![r=4\text{ percent}](https://img.qammunity.org/2023/formulas/mathematics/college/o6i9uqz1b0k51m72kt71aookilujydrszf.png)
We will need the interest rate in decimal form, for that, divide the percentage amount by 100:
![\begin{gathered} r=(4)/(100) \\ \downarrow \\ r=0.04 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/2qww8jgfi0fyx5x71oq4e8rirboclbuhc1.png)
And the time of the loan is 6 years, this will be the value of t:
![t=6](https://img.qammunity.org/2023/formulas/mathematics/high-school/7v1e6tmg2tu7i1dy00e94g2cw57i1tnuqe.png)
Step 2. To solve part a, we use the following formula to calculate the interest:
![I=p* r* t](https://img.qammunity.org/2023/formulas/mathematics/college/tmquigvsh5a8fo3z7iwdgqv19wc02etm36.png)
Substituting all of the known values:
![I=8,000*0.04*6](https://img.qammunity.org/2023/formulas/mathematics/college/h1zcn1qu73v2wtymoj0d6jupm3g9q46wpt.png)
The result is:
![I=1,920](https://img.qammunity.org/2023/formulas/mathematics/college/ls9w2okuro6zgxsr1tmn1iuqlc9ggs4tgz.png)
The total interest that Karen will have to pay is $1,920.
Step 3. To solve part b, we need to find the total repayment amount.
To find this, we add the interest and the principal amount:
![T=P+I](https://img.qammunity.org/2023/formulas/mathematics/college/s0vp5i5mcu3zmqjczrusy45l1etk7cpr1h.png)
Where T represents the total amount.
Substituting P and I:
![\begin{gathered} T=8,000+1,920 \\ \downarrow \\ T=9,920 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/ifnan4yxgda1vxerek8c02wnc48lpp6k9r.png)
The total amount she will have to repay is $9,920.
Answer:
a) $1,920
b) $9,920