What's HCF/GCD of 144 and 0 ?

Having a hard time understanding this question (see attachment).

The four students in the table below each recorded the time and distance traveled while exercising. exercising distance (miles) time (minutes) gia 2 30 harris 5 50 ian 3 40 jackson 4 80 which list ranks the students from fastest walker to slowest walker? jackson, gia, ian, harris harris, jackson, ian, gia harris, ian, gia, jackson jackson, harris, ian, gia

G. how many different 6-letter arrangements can be formed using the letters in the word absent, if each letter is used only once? a. 6 b. 36 c. 720 d. 46,656