Do the calculation !!

this is a non trick question.
The answer is not 0 and there is no extra two legs because of the bus driver!
there are seven girls.
each girl has 7 backpacks.
in each backpack are seven big cats.
with each big cat there is 7 small cats!
how many legs are there on the bus?
the answer is the code to open the excel document. put your name down on it and the date that you did it!