Solve the following sql problem:
Which biwords pair has a higher occurrence, "àbac-xinès" or "àbac-grec"?

Schema:
SCHEMA:
- Table: langs
  - Column: lid
    - Samples: [1]
  - Column: lang
    - Samples: [ca]
  - Column: locale
    - Samples: [ca_ES]
  - Column: pages
    - Samples: [1129144]
  - Column: words
    - Samples: [2764996]
- Table: pages
  - Column: pid
    - Samples: [1, 2, 3, 4, 5]
  - Column: lid
    - Samples: [1, 1, 1, 1, 1]
  - Column: page
    - Samples: [1, 2, 8, 9, 10]
  - Column: revision
    - Samples: [28236978, 24086480, 26230310, 28374033, 28336725]
  - Column: title
    - Samples: [Àbac, Abadia, Adagi, Adam, Addicció]
  - Column: words
    - Samples: [1081, 68, 304, 453, 1468]
- Table: words
  - Column: wid
    - Samples: [1, 2, 3, 4, 5]
  - Column: word
    - Samples: [àbac, xinès, llatí, grec, antic]
  - Column: occurrences
    - Samples: [242, 16841, 48700, 49897, 60220]
- Table: langs_words
  - Column: lid
    - Samples: [1, 1, 1, 1, 1]
  - Column: wid
    - Samples: [1, 2, 3, 4, 5]
  - Column: occurrences
    - Samples: [242, 16841, 48700, 49897, 60220]
- Table: pages_words
  - Column: pid
    - Samples: [1, 1, 1, 1, 1]
  - Column: wid
    - Samples: [1, 2, 3, 4, 5]
  - Column: occurrences
    - Samples: [30, 8, 2, 5, 2]
- Table: biwords
  - Column: lid
    - Samples: [1, 1, 1, 1, 1]
  - Column: w1st
    - Samples: [1, 1, 1, 1, 1]
  - Column: w2nd
    - Samples: [2, 4, 25, 34, 51]
  - Column: occurrences
    - Samples: [4, 3, 13, 29, 14]

SELECT CASE WHEN ( SELECT occurrences FROM biwords WHERE w1st = ( SELECT wid FROM words WHERE word = 'àbac' ) AND w2nd = ( SELECT wid FROM words WHERE word = 'xinès' ) ) > ( SELECT occurrences FROM biwords WHERE w1st = ( SELECT wid FROM words WHERE word = 'àbac' ) AND w2nd = ( SELECT wid FROM words WHERE word = 'grec' ) ) THEN 'àbac-xinès' ELSE 'àbac-grec' END AS CALUS FROM words LIMIT 1