A salesman normally gets a fixed salary of $500 and a commission of 5

From the question stem, we have the following information about the Salary of the Salesman
Before March
Fixed salary : 500$
Commission : 5% over 1000$ sales

(1) In March, the salesman had received a fixed salary of $600 and a commission of 4 percent on sales above $800.
In March(after salary revision)
Fixed Salary : 600$
Commission : 4% over 800$ sales
Since we don't know what the salary earned by March, we cannot tell what were his sales.(Insufficient)

(2) In March, he received $104 more than he would have received according to his earlier pay structure.
Since we no idea about the new salary structure, we cannot tell the exact sales. Insufficient.

On combining both the statements,
If her salary post the March increase, the increase in salary is 104$ more.
Case 1:
Sales before March : 600$. Salary received : 500$(Fixed)
Sales in March : 900$. Salary received : 600$(Fixed) + 4%(of Salary over 800$) = 604
Difference in Salary : 104$

Case 2:
Sales before March : 1200$. Salary received : 500$(Fixed) + 5%(of Salary over 1000$) = 500 + 10 = 510
Sales in March : 1150$. Salary received : 600$(Fixed) + 4%(of Salary over 800$) = 600 + 14 = 614
Difference in Salary : 104$

Since we have different values of Sales in both the cases, but the same difference in their salaries.
The combination of the statements is not enough. Insufficient(Option E)