Calculation of amount of the adjusting entry for office supplies on March 31:
It is given that office supplies account balance on March 1 was $1,400, the company purchased $675 of supplies during the month, and a physical count of supplies on hand at the end of March indicate $1,250 unused. It means the Supplies used was (1400+675-1250) = $825
Hence, the amount of the adjusting entry for office supplies on March 31 shall be $825.