To calculate $b$ from the provided image, I need some additional information or context. Specifically:

1. Is $b$ referring to the area of the yellow hexagon, the number of sides, or something else?
2. Are there any given dimensions, angles, or mathematical relationships that you know about this figure (e.g., relationships between $a$, $b$, and $c$)?

Please provide more details about the problem or clarify the exact nature of what $b$ represents. Alternatively, if this is part of a larger problem or topic, feel free to include relevant equations or details!

Let me know how you’d like to proceed.