I'm really struggling to answer questions A and B.

Bob went to the Academic Success Center(ASC) to get help on homework. One question he got was below:


"Q: Use inductive reasoning to determine the units digit of the number 3^55 . Please give detailed descriptions on how you would solve this problem."


Bob said he could use his high-precision calculator to find the exact value of 3^55, and he would know all the digits. He then showed Ali, the tutor his calculator display 3^55 = 1744492 1100912017 9071170507. The tutor Ali at the ASC said that was the incorrect approach to this problem.


(a) Why did Ali say it was an incorrect approach?


(b) What is the correct approach to get the answer of units digit =7? Be specific with how you solved this question.