#### Answer

$\frac{16}{81}a^{12}b^{28}c^4$

#### Work Step by Step

Use the outside exponent on each number within the parentheses. Remember to multiply the exponents of the bases by the outside exponent. In this case, we are multiplying $3$ by $4$, $7$ by $4$, and $1$ by $4$ for $a$, $b$, and $c$, respectively.
$(\frac{2}{3}a^3b^7c)^4$
$\frac{16}{81}a^{12}b^{28}c^4$