29-Q21这题怎么算出来的呢

Q21:

A toy store’s
gross profit on a computer game was 10 percent of the cost of the game.  If the store increased the selling price of
the game from $44 to $46 and the cost of the game remained the same, then the
store’s gross profit on the game after the price increase was what percent of
the cost of the game?

A.  
10.5%

B.  
11%

C.  
12.5%

D.  13%

E.  
15%        

Answer:

before the price raise, selling price 44, cost 40, profit 4

after the price raise, selling price 46, cost 40, profit 6

6/40 = 15%