Explanation:

- Option 1: To determine the number of workers to be employed

- Time study helps assess how long it takes to complete a task.

- This data can guide decisions on staffing levels.

- Option 2: To formulate suitable incentive schemes

- By understanding task duration, fair and motivating incentive schemes can be designed.

- It rewards workers based on performance and efficiency.

- Option 3: To calculate the labour costs

- Time study identifies standard times for tasks.

- This information is crucial for accurate labor cost estimation.

- Option 4: All of the above

- Time study's objective encompasses determining workforce needs, designing incentives, and estimating costs.

- It aims to improve productivity and efficiency through comprehensive analysis.

Correct Answer: Option 4 - All of the above