How do we know whether the value is negative or positive?? Please give clear explanation along with formula??

A project will incur 3600 in shutdown costs the year after the completion of the project. The tax rate is 40%. What is the value of the after-tax shutdown costs (where a negative number is a net cash outow and a positive number is an incremental cash inow)? Equipment with a book value of $6,000 will be sold at the end of a project for a salvage value of $9,000. The tax rate is 45%. What is the tax effect resulting from the prot or loss from the sale of the equipment (where a negative number means tax is payable and a positive number means that there is a tax shield)