= Solution
The <Quantum effective action> contains the following <Feynman diagram>[diagrams]. For $\Gamma_2$, there are the tree inverse propagator, the one-loop tadpole at order $\lambda$, and at order $\lambda^2$ the two-loop sunset and the two-loop tadpole with a tadpole insertion. For $\Gamma_4$, there are the tree vertex $-i\lambda$ and, at order $\lambda^2$, the three one-loop bubble diagrams in the $s$, $t$, and $u$ channels. Disconnected and one-particle-reducible graphs do not occur in the quantum effective action.
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