Answer:
1.- overhead rate: 1.2 dollars per material cost
2.- applied overhead: 822,000
underapplied 8,000
3.-
COGS 8,000 debit
Factory Overhead 8,000 credit
Step-by-step explanation:

the predetermined overhead rate divide the expected cost over a cost driver:
overhead cost: 750,000
cost driver: material cost: 625,000
rate: 750,000/625,000 = 1.2
each dollar of material cost will appliy 1.2 dollars of overhead.
applied overhead:
685,000 x 1.2 = 822,000
actual overhead: 830,000
underapplied 8,000
the applied overhead is lower than the actual cost, we must increase the capitalized cost.
The adjusting entry will increase overhead and COGS.