To answer this question we can propose the following equation:

Where:
x is the number of weeks elapsed.
d is the debt depending on the weeks.
Robert promised to pay at least $ 67 each week.
Therefore, after 5 weeks the debt of rober should be:


Then scenario A) is possible because
.
After 6 weeks:


Then scenario B) is possible because
.
After 7 weeks


Then scenario C) is possible because
.
After 8 weeks


So scenario D) is NOT possible because 
Finally the correct answer is option D.
79.56 would be the answer, (i’m pretty positive) because you take all three numbers and you multiply them together.
Let a ∈ A. Then a is some integer that is divisible by 4, so we can write a = 4k for some integer k.
We can simultaneously rewrite a as a = 2•2k, so 2 clearly divides a, which means a ∈ B as well.
Therefore A ⊆ B.