Calculated based on the final regulations sections 1.199A-1 through 1.199A-6, issued several days ago, it would be 20% of $1,646 ($5,000 - $3,000 - $354). This is how TurboTax does the calculation. $354 is the deductible portion of SE taxes for someone who has not maxed out the Social Security wage base.
The above also assumes that your taxable income is under the limit where being a specified service trade or business might be an issue and that you have taxable income of more than $1,646.