Answer: This is a violation of position limits
Step-by-step explanation:
When checking to see if there has been a violation of control limits, all the accounts managed by a single entity or all accounts under common control will be added up instead of being evaluated on an individual basis.
John manages 25 accounts out of which he bought calls for 10. He bought 30,000 for each of the 10 which would mean that he bought 300,000 call contracts.
This exceeds the 250,000 contract limit so is a violation of position limits.