Answer
A firm would shutdown temporarily if their total revenue is lower than their variable costs.
Work Step by Step
If total revenue would be higher than the firm's variable cost, it would be worth it for the firm to open. That is because even though the firm might not generate profit, it would still be better off than if it didn't open. If total revenue is higher than the variable cost, at least the firm is generating some revenue that can cover its fixed costs.
