Answer:
the question is not complete, but I believe it asks for the tax liability if Ms. Diaz files as single filer or surviving spouse:
using the 2020 tax brackets
single filer:
Ms. Diaz's marginal tax rate is 35%, and her tax liability = $47,367.50 plus 35% of the amount over $207,350 = $47,367.50 + [($219,344 - $207,350) x 0.35] = $50,565.40
surviving spouse or married filing together:
Ms. Diaz's marginal tax rate is 24%, and her tax liability = $29,211 plus 24% of the amount over $171,050 = $29,211 + [($219,344 - $171,050) x 0.24] = $40,801.56
Ms. Diaz will be considered a surviving spouse for 2 years after her husband passed away.