Final answer:
If Midori and Tremaine qualify for a $1900 refundable tax credit, their tax bill will be reduced by $1900.
Step-by-step explanation:
Midori and Tremaine are in the 24% tax bracket, file jointly, and take the standard deduction. A tax credit is a direct reduction in the amount of tax owed, so it will reduce their tax bill dollar for dollar. If they qualify for a $1900 refundable tax credit, their tax bill will be reduced by $1900.