Answer:
Consumer Surplus for Brent is lowest among the three
Step-by-step explanation:
Given;
Price of electric sharpener = $20
Brent’s willingness to pay = $22
Callie’s willingness to pay = $25
Danielle's willingness to pay = $30
Now, 
The Consumer surplus is calculated as:
= Maximum price a consumer is willing to pay - Actual price 
Therefore,
Consumer Surplus for Brent = $22 - $20 = $2 
Consumer Surplus for Callie = $25 - $20 = $5 
Consumer Surplus for Danielle = $30 - $20 = $10
Therefore,
The Consumer Surplus for Brent is lowest among the three