Answer:
Option C. exponential decay function
Step-by-step explanation:
In this problem we have a exponential function of the form

where
y ---> is the money that is in the bank
x ----> number of days
a ---> is the initial value or y-intercept
b is the base of the exponential function
r ---> is the rate of change
b=(1+r)
In this problem we have that
Each day 1/2 of the money that is in bank value is removed
so
---> is negative because is a decreasing function
The value of b is equal to


The value of b is less than 1
b<1
That means -----> Is a exponential decay function
Simply take the numerator (3) and denominator (7) and add them together.
3+7 = 10, which means that the ratio will provide parts that are in multiples of 10 depending on the total
so take 10x = 800
x = 80.
Then multiply this by the numerator and denominator
3*80/7*80 = 240/560.