Answer:
80 or 81
Step-by-step explanation:
Now, let's do the same as we did for the previous one here.

notice again, how did we get 84 for the 4th element's coefficient? well 36 * 7 / 3. and so on. And you can just expand it from there.
B 6.44 because 6.4 is equal to 6.40 and in between 6.40 and 6.60 there is 6.44.