A software company's user base grows according to $U_n = 1.2 U_{n-1} + 5000$, where $U_n$ is the user count at the end of month $n$, with $U_0 = 10,000$.

The general solution is $U_n = U_n^{(h)} + U_n^{(p)} = c \cdot 1.2^n + U_n^{(p)}$. What is the particular solution $U_n^{(p)}$?