Explanation

6 persons working 8 hours a day earn Rs. 8400 per week.

First, let's calculate the total hours worked by 6 persons in a week:

6 persons x 8 hours/day x 7 days/week = 336 hours/week

Now, let's calculate the total amount earned per hour:

Rs. 8400 per week ÷ 336 hours/week = Rs. 25 per hour

Now, let's calculate the total hours worked by 9 persons in a week:

9 persons x 6 hours/day x 7 days/week = 378 hours/week

Finally, let's calculate the total amount earned by 9 persons in a week:

378 hours/week x Rs. 25 per hour = Rs. 9450 per week

So, the correct answer is: Rs. 9450