We have the expression
[tex]40(10)^{3t}[/tex]
To solve it we must remember the property:
[tex](a^m)^n=(a)^{m\cdot n}[/tex]
Here we have
[tex]40(10)^{3\cdot t}[/tex]
Using the property it will be
[tex]40(10^3)^t[/tex]
Now we solve it inside the parenthesis
[tex]40(1000)^t[/tex]
Therefore r = 1000, the correct answer is the letter C.
