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: What is the number of centimeters in the length of $EF$ if $AB\parallel CD\parallel EF$?

[asy]

size(4cm,4cm);
pair A,B,C,D,E,F,X;

A=(0,1);
B=(1,1);
C=(1,0);
X=(0,0);
D=(1/3)*C+(2/3)*X;

draw (A--B--C--D);
draw(D--B);
draw(A--C);

E=(0.6,0.4);
F=(1,0.4);

draw(E--F);

label("$A$",A,NW);
label("$B$",B,NE);
label("$C$",C,SE);
label("$D$",D,SW);
label("$E$",shift(-0.1,0)*E);
label("$F$",F,E);

label("$100$ cm",midpoint(C--D),S);
label("$150$ cm",midpoint(A--B),N);

[/asy]
user