How to file dual status tax return? (The year from F1 visa to H1B)

I was on F1 visa from Jan to Sep 2020 and on H1B visa from Oct to Dec 2020. I did some research and would like to file a dual-status tax return this year.

 

My question is if I file 1040 NR for Jan to Sep, and 1040 for Oct to Dec, how do I determine the taxable rate? Since my taxable income in either status would be much lower than my actual annual income.

 

10%

Up to $9,875

12%

$9,876 to $40,125

22%

$40,126 to $85,525

24%

$85,526 to $163,300

 

Thanks