Greg, a self-employed plumber, commutes from his home to his office which is 10 miles away. at his office, he loads his truck for the day with the parts that he needs. then he is off to see his first customer of the day, mr. smith. mr. smith is 5 miles away from the office. after mr. smith's job, greg goes to his next plumbing client, martin's dry cleaning, which is 21 miles away from mr. smith. greg spends the rest of the day at martin's dry cleaning. from martin's dry cleaning, greg goes home which is now only 7 miles away. how much can greg count as deductible transportation miles?