Explanation:

- Let the incomes of the two employees be 7x and 4x.

- Let their expenditures be 3y and y.

- Savings for both: Income - Expenditure = 4,800.

- For the first employee: $7x-3y=4,800$.

- For the second employee: $4x-y=4,800$.

- Solving the two equations:

- From $4x-y=4,800$, we get $y=4x-4,800$.

- Substitute $y=4x-4,800$ in $7x-3y=4,800$.

- Solve for x to find the values.

Correct calculations give the solution:

- Total income = $7x+4x=11x$.

- Calculated x gives a correct monthly total income of: ?21,120.

- This corresponds to Option 1: 21,120.

The correct answer is Option 1: 21,120.

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