Determine the amount of the standard deduction for each of the following taxpayers for tax year 2018:

a. Christina, who is single.

b. Adrian and Carol, who are filing a joint return. Their son is blind.

c. Peter and Elizabeth, who are married and file separate tax returns. Elizabeth will itemize her deductions.

d. Karen, who earned $1,100 working a part-time job. She can be claimed as a dependent by her parents.

e. Rodolfo, who is over 65 and is single.

f. Bernard, who is a nonresident alien with U.S. income.

g. Manuel, who is 70, and Esther, who is 63 and blind, will file a joint return.

h. Herman, who is 75 and a qualifying widower with a dependent child.