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Exhibit 10.5

AMENDMENT NO. 4
TO
COST ALLOCATION AGREEMENT

WHEREAS, Zenith National Insurance Corp., Zenith Insurance Company, ZNAT
Insurance Company, CalFarm Insurance Company, CalFarm Insurance Agency, Zenith
Star Insurance Company, and Zenith Insurance Company of Florida have previously
entered into a Cost Allocation Agreement; and

WHEREAS, effective June 30, 1998, Zenith Insurance Company of Florida has been
merged with Zenith Insurance Company and Zenith Insurance Company is the
surviving corporation;

IN CONSIDERATION OF THE PREMISES, the parties agree as follows:

1.Effective June 30, 1998, Amendment No. 3 to the Cost Allocation Agreement is
terminated.

2.In all other respects the Cost Allocation Agreement remains unchanged,

IN WITNESS WHEREOF, each of the undersigned parties has caused this Amendment
No. 4 to be executed on its behalf, this 15th day of July, 1998.

              ZENITH NATIONAL INSURANCE CORP.   ZENITH INSURANCE COMPANY        
      By:   /s/  JOHN J. TICKNER      

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  By:   /s/  JOHN J. TICKNER      

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              ZENITH STAR INSURANCE COMPANY   CALFARM INSURANCE COMPANY        
      By:   /s/  JOHN J. TICKNER      

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  By:   /s/  JOHN J. TICKNER      

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              CALFARM INSURANCE AGENCY   ZNAT INSURANCE COMPANY              
By:   /s/  JOHN J. TICKNER      

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  By:   /s/  JOHN J. TICKNER      

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AMENDMENT NO. 4 TO COST ALLOCATION AGREEMENT