<s>[INST] Let $a,b,c,d,e,f,$ be positive integers such that $a\ge b\ge c\ge d\ge e\ge f.$ Suppose that \begin{align*} 3a+2b+c &= 9000, \\ 3a+2b+c &= 11D+L \text{, where L = remainder}, \\ d+2e+f &= 900. \end{align*} What is the value of $a-b$?[/INST]