Final answer:
To find the APR using a spreadsheet, you can use the RATE function. The calculated APR is approximately 6.78% (b).
Step-by-step explanation:
To find the APR using a spreadsheet, you can use the RATE function. The RATE function calculates the annual interest rate for a loan with a fixed payment and constant interest rate. In this case, the loan amount is $20,000 (balance after down payment), the payment amount is $300, and the number of periods is 48 (4 years x 12 months).
To calculate the APR, you can use the formula: =RATE(48, 300, -20000).
The calculated APR is approximately 6.78%. So the correct answer is b) 6.78%.