Final answer:
Riley will earn a total of $2,706.86 in 15 years.
Step-by-step explanation:
To calculate the total amount Riley will earn in 15 years, we need to use the compound interest formula: A = P(1 + r/n)^(nt), where A is the total amount, P is the principal (initial investment), r is the interest rate, n is the number of times interest is compounded per year, and t is the number of years.
In this case, P = $1,000, r = 6.75% = 0.0675, t = 15 years, and n = 2 (compounded semi-annually).
Using these values, the total amount Riley will earn is: A = $1,000(1 + 0.0675/2)^(2*15) = $2,706.86.
Therefore, the correct answer is c) $2,706.86.