The total ISR instruction count for interrupt A, interrupt B, and interrupt C are 90, 150, and 120 instructions, respectively. Interrupt A occurs thrice as often as interrupt B, while interrupt C is called once whenever the other interrupts are called. If our microcontroller executes 60 million instructions per second and the combined CPU percentage of the three interrupts is 20% assuming they do not interrupt each other.

What is the CPU overhead of interrupt B alone?