In a , the price stated in the agreement does not change, regardless of fluctuations in general overall economic conditions, industry competition, levels of supply , market prices, or other environmental changes.

The correct word for the blank space is: fixed-price contract.

Explanation:

Fixed-price contracts are those in which a fixed amount is set at the beginning of the work that will be done. The advantage and disadvantages of this type of contract depend on market fluctuations. If the prices of the materials used for the work drop, for instance, the individual performing the work will be at advantage. If the prices rise, instead, that individual would be at a disadvantage.

The fixed-price contract opposes the cost-plus contract since the latter reports the expenditures incurred and price to be charged at the end of the work.

b. take periodic breaks and alternate between tasks.  

will increase work efficiency, and avoid health issues.