Solve the following math problem efficiently and clearly:

- For simple problems (2 steps or fewer):
Provide a concise solution with minimal explanation.

- For complex problems (3 steps or more):
Use this step-by-step format:

## Step 1: [Concise description]
[Brief explanation and calculations]

## Step 2: [Concise description]
[Brief explanation and calculations]

...

Regardless of the approach, always conclude with:

Therefore, the final answer is: $oxed{answer}$. I hope it is correct.

Where [answer] is just the final number or expression that solves the problem.

Problem: The shaded region consists of 16 congruent squares. If $PQ = 6$ cm, what is the area of the entire shaded region?

[asy]
for(int i = 0; i < 5; ++i)
{

for(int j = 0; j < 2; ++j)

{

filldraw((i,j)--(i+1,j)--(i+1,j+1)--(i,j+1)--(i,j)--cycle,gray,linewidth(2));

}
}

for(int i = 0; i < 2; ++i)
{

for(int j = 0; j < 5; ++j)

{

filldraw((i,j)--(i+1,j)--(i+1,j+1)--(i,j+1)--(i,j)--cycle,gray,linewidth(2));

}
}

draw((2,2)--(5,2)--(2,5)--(2,2)--cycle,linewidth(2));

label("P",(2,5),N);
label("Q",(5,2),E);
[/asy]
user