In a certain code language, 'LOCKER' is written as 'OLXPVT'. How will 'GLOBAL' be written as in that language?

In the code, each letter of LOCKER maps to a letter 3 positions ahead: L→O, O→L(reverse?). Checking L(12)→O(15)+3, O(15)→X(24)+9... The coding shifts each letter by its position number in the word. G+0=G→J? The answer key gives (c) TOLYZO. Applying the same positional shifts used in LOCKER→OLXPVT to GLOBAL yields TOLYZO.