Molly always deposit more $40 while Vitto always duplicate the money, so we can withdray 2 equations
For Molly: $ = 40.n 
For Vitto: $ = 

where n is the month number and $ the money
So, we can say?

Look, in the 10th month, Vitto will have 
=512 while Molly will have 40.10 = 400
So, Vitto's balance will be greater after a very long time. A.