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: Bag A has 3 white marbles and 4 black marbles.  Bag B has 6 yellow marbles and 4 blue marbles.  Bag C has 2 yellow marbles and 5 blue marbles.  A marble is drawn at random from Bag A.  If it is white, a marble is drawn at random from Bag B, otherwise, if it is black, a marble is drawn at random from Bag C.  What is the probability that the second marble drawn is yellow?
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