Answer:
Sarah earns R6 100 in total for her work to the value of R12 000.
Explanation:
To calculate Sarah's earnings, we need to break down her income into two parts: the commission she earns on income up to R5 000, and the bonus commission she earns on income above R5 000.
Commission on income up to R5 000:
Sarah's basic salary is R3 000 per month, and she earns 20% commission on income up to R5 000. So for the first R5 000 of income, Sarah's commission is:

Bonus commission on income above R5 000:
Sarah also receives a 10% bonus on top of the normal commission rate on earning above R5 000. So for the amount earned above R5 000, her commission is:

Total earnings:
Sarah's total earnings are the sum of her basic salary and the commission she earns:
Total earnings = Basic salary + Commission on income up to R5 000 + Commission on income above R5 000


Therefore, Sarah earns R6 100 in total for her work to the value of R12 000.