Brain weight B as a function of body weight W in fish has been modeled by the power function B = 0.007W2/3, where B and W are measured in grams. A model for body weight as a function of body length L (measured in centimeters) is W = 0.12L2.53. If, over 10 million years, the average length of a certain species of fish evolved from 13 cm to 22 cm at a constant rate, how fast was this species' brain growing when the average length was 18 cm? (Round your answer to four significant figures.)

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