Answer:
Part a) The constant of variation is
or

Part b)
Explanation:
Part a) Find the constant of variation.
we know that
The simple interest formula is equal to
In this linear direct variation the constant r represent the constant of proportionality
where
I is the Interest Value
P is the Principal amount of money to be invested
r is the rate of interest
t is Number of Time Periods
in this problem we have
substitute the values and solve for r


Part b) what will the interest be after 3 years
in this part we have
substitute the values