Under a system of dual federalism, conflicts between state laws and federal laws are a. inconsequential b. common c. unconstitutional d. uncommon

B. Common

Dual federalism is a system which divides and delineates powers between federal and state governments.  The fact that such powers are defined and delineated does not mean that the states and the federal government will remain in harmony over areas of jurisdiction.  Dual federalism intends to treat states and the federal government as co-equal sovereign powers, which means that those two powers will inevitably come into conflict with one another over issues that have pertinence beyond the borders of any one state.

We know from the question that Store A charges $1200 for repairs and 6% as sales tax.
Then
Amount of sales tax charged by Store A = (6/100) * 1200
                                                                 = 6 * 12
                                                                 = 72 dollars
Then the total amount charged by Store A = ( 1200 + 72) dollars
                                                                   = 1272 dollars
Now coming to Store B. It charges $1350 for repairs and 7% of sales tax.
Amount of sales tax charged by Store B = (7/100) * 1350
                                                                 = 945/10
                                                                 = 94.5 dollars
Then the total amount charged by Store B = ( 1350 + 94.5) dollars
                                                                     = 1444.5 dollars
Amount of money saved by choosing Store A instead of Store B = (1444.5 - 1272) dollars
                                                                                                       = 172.5 dollars
So $172.5 is saved by choosing Store A over Store B.