Answer:
Order size= $57.61 per machine hour
Step-by-step explanation:
Giving the following information: 
Order size:
Estimated total overhead= $581,866 
Estimated total machine hours= 10,100 
To calculate the predetermined manufacturing overhead rate we need to use the following formula:
Predetermined manufacturing overhead rate= total estimated overhead costs for the period/ total amount of allocation base
Order size= 581,866 / 10,100
Order size= $57.61 per machine hour