Answer :
The average profit (or loss) is found by adding up the profits (or losses) of the past 5 months and divinding the resulting amount by 5 (the number of months). The account is [85 + 70 + 120 + 90 + 35] / 5 = 80. Then the answer is the option C or D. HIs average loss was $80 per month or His average profit was $80 per month.