Instead of guessing a formula and checking it against every letter, treat the six known pairs as points on a line and find that line's equation directly, using each letter's alphabet position as \( n \) and its code as \( f(n) \).
M is the 13th letter and codes to 79, and A is the 1st letter and codes to 7. Assuming a straight-line relationship \( f(n) = mn + k \), these two points give:
\[ m = \frac{79 - 7}{13 - 1} = \frac{72}{12} = 6 \]
\[ k = 7 - 6 \times 1 = 1 \]
So \( f(n) = 6n + 1 \).
All six letters of MASTER fit \( f(n) = 6n + 1 \) exactly, confirming the rule. Now apply it to LAUGH:
So LAUGH is coded as 73 7 127 43 49.
