QUESTION:int mystery(int level, int x) {
   if(level == 0) {
      return NUM;
   } else {
      int r = CALL;
      return COMBO;
   }
}
What is the result of mystery(3, 5);
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RECURSION:CALL|CALL OP TERM
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CALL:mystery(level - 1, XEXP)
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COMBO:REXP OP XEXP
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XEXP:x|x OP XEXP|x OP NUM
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REXP:r|r OP REXP|r OP NUM
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NUM:1|5
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OP:+|-|*|%|/
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