Musk, who is CEO of both companies, says there is "a lot to be gained" from the merger, which would be the biggest in history.
The prime minister provided little detail, and there are questions over shifting the fees onto unit costs.
Kashim Chowdhury was contracted for 183 hours a week, more than the number of hours in seven days.
The economic figures released on Wednesday show the constraints for John Healey as he puts the finishing touches to his Budget.
UK inflation rose in September, pushed up by higher petrol and diesel prices.
Inflation accelerated to 3.5% from 3.1% in the year to September, according to the Office for National Statistics (ONS).
Investigative genetic genealogy can help hunt down criminals but raises worries over privacy.
Musk says a mega merger would have many benefits to his companies.
No formal investigation has started, but the regulator is making inquiries into the case.