To find Joan's net pay, we need to subtract all the deductions from her gross pay.
- Gross Pay: $400
- Total Deductions:
- OASDI: $24.80
- Medicare: $5.20
- Income Tax: $45
Now, let's add up the deductions:
\[ 24.80 + 5.20 + 45 = 75 \]
Now, subtract the total deductions from the gross pay:
\[ 400 - 75 = 325 \]
Therefore, Joan's net pay is $325.
The correct answer is A. $325.