Discuss the advantages and disadvantages of authoritative budgeting and particip

Discuss the advantages and disadvantages of authoritative budgeting and participative budgeting. Why an effective budget process usually combines both?
First Please explain Authorative budgeting and Participative budgeting. 
Then, 
Advantages of Participative Budgeting: 
Disadvantages of Participative Budgeting
Advantages of Authoritative Budgeting:
Disadvantages of Authoritative Budgetig
why effective budget process usually combines both ?