Answer:
option (b) $69,768 
Explanation:
Data provided in question:
Estimated manufacturing overhead = $73,440
Estimated machine-hours = 1,800 
Actual manufacturing overhead = $68,700
Actual machine-hours = 1,710
now,
The predetermined overhead rate =  
or
The predetermined overhead rate =  
or
The predetermined overhead rate = $40.8 per hour
Therefore,
The applied manufacturing overhead for the year
=  Actual machine-hours × predetermined overhead rate
= 1,710 × $40.8
= $69,768
Hence,
the correct answer is option (b) $69,768