11. (10 points) In the game "Temple Run", eating a yellow coin earns 1 yuan; eating a red coin earns 3 yuan; eating a blue coin earns 5 yuan. It is known that Archie ate a total of 2800 coins in one game, earning a total of 7800 yuan, and the number of blue coins he ate was 200 more than the number of red coins. How many red coins did Archie eat?
A. 700
B. 900
C. 1200
D. 1500
【Solution】Solution: According to the analysis, subtract the 200 more blue coins than red coins from the total, which gives us: $2800-200=2600$ coins,

The total amount obtained is: $7800-5 \times 200=6800$ yuan. After making the number of red and blue coins the same, we can consider there are two types of coins: one is the 1 yuan yellow coin,

and the other is: $(3+5) \div 2=4$ (yuan) for the red and blue coins. Assuming all 2600 coins are 1 yuan each, the number of red and blue coins together is: $(6800-2600 \times 1) \div(4-1)=1400$ (coins), so the number of red coins is: $1400 \div 2=700$ (coins). Therefore, the answer is: A.