Don and Deirdre are married but they have not lived together for the last three years. Don and Deidre are not legally separated and she will agree to file a joint return. For the past two years Dons father Wyatt has lived with him. Wyatts only income is a pension of $2,500 and social security of $3,950. Don pays all the costs of keeping up the home and can claim Wyatt as a dependant. Son has no other dependents and no one else lived in the home. What is Dons filing status?