Answer:
$33
Step-by-step explanation:
First we calculate the cost of the overdrafts:
3 overdrafts * $35 = $105
Then, if he maintains an average monthly balance of $600, we can calculate = $600*12 months = $7200 (average yearly balance). And the bank pays him 1% interest per annum:
$7200 * 1% = $72 (this is what the bank pays the graduate per year)
So if the bank charges him $105 and pays him $72, then the net annual cost is = $105-$72= $33