On the Subject of the McDondald's™ Chicken Nugget Big Mac CM

A machine that knows no bounds when it comes to ciphers.

From the Off-White Cipher module by TandyCake, Dicey, and Diffuse.

You’re currently working at McDondald's™ and you can only sell Chicken Nuggets and Big Macs. Screen 1 displays the price of a Big Mac. Screen 2 displays the price of a box of Chicken Nuggets. Convert both of these prices from dollars to cents (1 dollar = 100 cents).

Split the encrypted word into letter pairs. Each of these three pairs corresponds to an order at McDondald's™, dictating the money paid. If the amount of letters in the encrypted word is odd, the last letter is an unfinished order because the customer couldn’t be bothered to show up. Leave this letter unchanged as a symbol of how lazy and incompetent people can be.

For each letter pair, do the following:

  • Convert the letters into their alphabetic positions. If the letter is a Z, its value is zero (A1Y25Z0). Add together the Nth letter of the order number on screen 4 (A1Y25Z0) times 676, the first letter of the pair times 26, and the second letter of the pair.
  • The value calculated is the amount paid for that order. With this information, it is possible to deduce the items ordered for each order.
  • For each amount paid, there are two corresponding letters. The first is the number of Chicken Nuggets ordered, converted to A1Y25Z0. The second is the number of Big Macs ordered, converted to A1Y25Z0. These numbers correspond to the decrypted letters for the Nth pair.

Tip: you can determine the number of Chicken Nuggets ordered by multiplying the amount paid by the number of pieces of Chicken Nuggets in a box displayed on screen 3, then moduloing by the price of the Big Mac. The number of Big Macs can be deduced with this value.

Example 1

Encrypted Word: ZVGRXGLQ
Screen 1: $3.78
Screen 2: $1.69
Screen 3: 85 Pc.
Screen 4: FGKC

F + ZV → (6 * 676) + (0 * 26) + 22 → 4078
(4078 * 85) MOD 378 → 4 → D
(4078 - D * 169) / 378 → 9 → I
G + GR → (7 * 676) + (7 * 26) + 18 → 4932
(4932 * 85) MOD 378 → 18 → R
(4932 - R * 169) / 378 → 5 → E
K + XG → (11 * 676) + (24 * 26) + 7 → 8067
(8067 * 85) MOD 378 → 3 → C
(8067 - 3 * 169) / 378 → 20 → T
C + LQ → (C * 676) + (12 * 26) + 17 → 2357
(2357 * 85) MOD 378 → 5 → E
(2357 - E * 169) / 378 → 4 → D

Decrypted Word: DIRECTED

Example 2

Encrypted Word: PWBVY
Screen 1: $3.45
Screen 2: $2.24
Screen 3: 134 Pc.
Screen 4: HM

H + PW → (8 * 676) + (16 * 26) + 23 → 5847
(5847 * 134) MOD 345 → 3 → C
(5847 - C * 224) / 345 → 15 → O
M + BV → (13 * 676) + (2 * 26) + 22 → 8862
(8862 * 134) MOD 345 → 18 → R
(8862 - R * 224) / 345 → 14 → N

Decrypted Word: CORNY