Final answer:
To adjust the sales price of the comparable property to reflect the value of an extra bedroom in the subject property, $20,000 should be added to the price of the comparable property.
Step-by-step explanation:
To determine the adjusted sales price of the comparable property with one bedroom when the subject property has two bedrooms and an additional bedroom is estimated to add $20,000 to the value, we would add $20,000 to the sales price of the comparable property. This is because the extra bedroom in the subject property increases its value compared to the comparable property. Therefore, the correct action would be option a) Add $20,000.