The cache is not at the posted co-ordinates.
Determine the letters represented by abc def and substitute their actual values in to the formula to reveal the caches' location co-ordinates.
Decryption Key
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
5 4 0 1 2 8 9 6 3 4 6 7 2 3 8 0 5 1 3 6 0 7 4 2 9 4
N 50 21.abc W 04 09. d(e-2)f
You can validate your puzzle solution with certitude.
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