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