Context-free Grammar for the language L=${w, epsilon left { a,b,c right }^{*} /w= a^{n} b^{2n+1} c^{n} a^{n-1} ,|,,n ge 2}$

I have been trying to find a context-free grammar for the language L=${w, epsilon left { a,b,c right }^{*} /w= a^{n} b^{2n+1} c^{n} a^{n-1} ,|,,n ge 2}$ for some time but I cannot get it done. Any ideas ?