The following reserves appear in the financial statements of B Ltd. for the current year:

• Allowance for doubtful accounts
• Warranty claims
• Contingent liability with respect to an upcoming union negotiation                                        
• Amounts due after the end of the year from merchandise sales with a three-year payment term

Which of the above reserves are deductible for tax purposes? Income tax reference: ITA 18(1)(e), 20(1)(l), 20(1)(n).