Kasey and Andrew each went for a walk once a day for 4 days. Kasey walked 3/4 miles each day. Andrew walked 3/5 mile each day. At the end of 4 days, how much farther in miles had Kasey walked than Andrew?
a) 0.6 miles
b) 0.8 miles
c) 1.2 miles
d) 1.6 miles