the difference from 40000 to the future value in 2020, namely 5 years later is simply the yield or interest amount.

Answer:
(-1,2)
Step-by-step explanation:
You can tell if two fractions are proportional by cross multiplying the fractions. If the fractions are equivalent, then they are proportional. If they are not equivalent, they are not proportional.
Step-by-step explanation:
I can only answer part 2 of your question, "If we multiply two positive numbers, is the result positive or negative?". if you multiply 2 positive numbers your answer would be positive.
The answer to your question is C.