Answer: contingent reward
Explanation:
From the question, we are informed that Cary just announced to his employees that if they meet the sales goal for the month of August, they can have a paid four-day vacation.
The style of leadership that is being used by Cary in this case is contingent reward. This is a type of style whereby there is a reward that is attached when the employees achieve a particular objective. This is typically done to motivate employees.