In regards to this answer, $ will be used to represent the currency of Bonanza.
For anyone in Bonanza who makes $90,000 or less, the tax liability rate is 5%. So an individual in this "bracket" would pay up to $4,500 in tax liability.
Anyone who makes over $90,000 up to and including $140,000, will still pay the 5% ($4,500) for $90,000 of their salary, but for the remaining salary, they will pay a tax liability of 15%. So, an individual making $140,000, would pay $4,500 + ($140,000 - 90,000)x0.15 which would equal $4,500 + $7,500 = $12,000. From a practice standpoint, it would be very painful to make slightly over $90,000!
Anyone who makes over $140,000 up to and including $220,000, will still pay the $12,000 on the first $140,000 of his/her salary, but for the remaining salary, will pay a tax liability of 25%. So, an indivudla making $220,000, would pay $12,000 + ($220,000 - $140,000)x0.25 which would equal $12,000 + $20,000 = $32,000.
Anyone who makes over $220,000 will still pay the $32,000 on the first $220,000 of his/her salary, but for the remaining slaary,w ill pay a tax liability of 0.35%. So, an individual making $300,000, would pay $32,000 + ($300,000 - $220,000)x0.35 = $32,000 + $28,000 = $60,000.
The tax function is step-wise and not continuous as there are breaks/plateaus in the function.