A salesperson earns a weekly base salary plus a commission of 20% of all sales over the first $500. This situation can be represented by the expression 750+0.2(x-500). Which of the following describes the meaning of 0.2(x-500) for this situation?a. total amount of salesb. total amount of salary earned c. total amount of sales after the first $500d. total amount of commission earned and example why it is the answer