Ben, age 67, and Karla, age 58, have two children who live with them and for whom they provide total support. Their daughter is 21 years old, blind, is not a full-time student and has no income. Her twin brother is 21 years old, has good sight, is a full-time student and has income of $4,500. They also support Ben's cousin who lives in another state. How many qualifying children or relatives can Ben and Karla claim