I've read the instructions for 1040 and Pub 519 several times but can't find the answer.  Where exactly did you find the instructions?  It doesn't say how you add up the tax liability.

I can only find the following (Pub 519, under Forms to File, Chp 6, Pg 34):

Resident at end of year. You must file Form 1040 or 1040-SR if you are a dual-status taxpayer who becomes a resident during the year and who is a U.S. resident on the last day of the tax year. Write "Dual-Status Return" across the top of the return. Attach a statement to your return to show the income for the part of the year you are a nonresident. You can use Form 1040-NR as the statement, but be sure to write "Dual-Status Statement" across the top.