3, 5 and 7 are three prime numbers. The least common multiple of prime numbers is simply the product of the numbers themselves: so you have

Answer:

Step-by-step explanation:
Given

Required
To determine if it is an exponential function, we have to write in form of

If we're able to do so, then the function is an exponential function.
If otherwise, then it is not

Apply Law of indices

Express 5^3 as 125

Factorize the exponent of 5

Express 5^2 as 25

This can be rewritten as:

By comparing the above to 
We have that


Since, we've be able to express the function as 
Then,
is an exponential function
16,404 feet is the answer