I need some help with the following question:
One of the languages
$$L_1 = \{a^pb^{q+r}c^sd^{q+t}e^{p+r} \mid p, q, r, s \ge 0\ , s > t\}$$ $$L_2 = \{a^{p+q}b^rc^sd^{q+r}e^s \mid p, q, r, s \ge 0\}$$
is context-free and the other is not. Build a context-free grammar for the one that is. For the other one provide a proof that it is not regular, or that it is not context-free.
How do I approach this problem ? I think that L2 is context-free because no comparisions are made. L1 is not context-free.
Thanks in advance