Finding the Modulus of a Complex Expression

Consider the complex number $z = 3 + 4i$. The objective is to find the modulus of the complex number $z^2 - 12z + 28$. To calculate the modulus, you will first need to expand the expression.

Recall that the modulus of a complex number $a + bi$ is given by the formula:

$$|a + bi| = ext{sqrt}(a^2 + b^2)$$

What is the modulus of the expression $z^2 - 12z + 28$?