Given data:
The initial numbers of follower areA=500,000.
The rate at which followers increases is r=19% =0.19.
(a)
The expression for the exponential growth model is,
Substitute the given values in the above expression.
(b)
The value of time is 7 in the year 2019, substitute 7 for t in the above expression.
Thus, the expression for the exponential model is f=500,000(1.19)^t, and the followers in the year 2019 is 1690,000.