We need to find the pattern for encoding the word "PUNCTUAL" into numbers. The corresponding code for each letter in "PUNCTUAL" is:
P = 4, U = 7, N = 8, C = 1, T = 9, U = 7, A = 6, L = 5.
So, the word "LUNA" corresponds to the letters:
L = 5, U = 7, N = 8, A = 6.
Therefore, the code for "LUNA" is 5786.