If there are roughly 140M jobs, presumably there are 140M people working those jobs, meaning that there are approximately 140M people who must cover that $6.4T, which works out to be ~$46k/yr for each working person.
If we assume we can completely wipe the following off the books: Social Security ($773M), Income Security ($541M) and Medicare ($471M), the net cost per year drops to $4.6T/yr, which works out to be ~$33k/yr for each working person.
Total federal income tax[1] in 2013 was around $1.3T (Individual) + $273B (Corporate) = $1.59T. An increase from $1.59T to $6.2T is about a 290% net increase.
I did some very rough spreadsheet-math with [2] and [3] and came up with the following. If we didn't tax the $20k at all, and left everything the same as last year, the bottom 77% would be a net negative of ~$1.2T assuming all of their income tax went directly to pay for the $20k.
I assumed that the number of people in the top 2% made the same average salary as the top 1% in [4], and came up with the top 2% of income tax payers as being a net positive of $1.4T. I made that assumption just to make the math easy and to err on the side of optimism.
The 78-98 percentile come out to be a net positive of approximately $350B.
Looking back at the $1.3T federal income tax total for individuals, this would mean that after the $20k/person was paid for, the total federal income tax dollars would be roughly $600B (Individual income tax) + $273B (Corporate income tax) = $873B.
Looking at [5], it seems that there was a $3.803T - $2.902T = $901B deficit last year. If we knock off the difference in income tax revenues ($1.59T - $873B = $717B), then suddenly we have a $901B + $717B = $1.618T deficit again.
This all assumes that jobs stay constant, of course. I realize that all of these numbers are very rough, but I had some fun doing spreadsheet math so I figured I would share!
[1] http://www.usgovernmentrevenue.com [2] http://en.wikipedia.org/wiki/Household_income_in_the_United_... [3] http://en.wikipedia.org/wiki/Rate_schedule_(federal_income_t... [4] http://www.cbo.gov/sites/default/files/cbofiles/attachments/... [5] http://en.wikipedia.org/wiki/2013_United_States_federal_budg...