According to the Aufbau Principle, the energy of atomic orbitals is determined by the $(n + l)$ rule:

1. Lower $(n + l)$ = Lower Energy.
2. If $(n + l)$ is equal, the orbital with the lower $n$ value has lower energy.

Analysis of given orbitals:

• 5f: $n=5, l=3 \implies (n+l) = 8$
• 6p: $n=6, l=1 \implies (n+l) = 7$
• 5p: $n=5, l=1 \implies (n+l) = 6$
• 4d: $n=4, l=2 \implies (n+l) = 6$

Ordering:

• Highest Energy: $5f$ (sum = 8)
• Second: $6p$ (sum = 7)
• Tie-break (5p vs 4d): Both have a sum of 6. The orbital with the higher $n$ (5p) has higher energy.
• $5p > 4d$

Final Decreasing Order: $5f > 6p > 5p > 4d$