In this equation, what is the value of $b$?

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According to a model, the estimated volume of a certain Douglas fir tree increases by 15.5% for every increase of 100 centimeters in the tree's height. The equation

y = a b^{\frac{x}{100}}

represents this model, where

y

represents the estimated volume, in cubic centimeters, of this Douglas fir tree,

x

represents the tree's height, in centimeters, and

a

and

b

are constants.

In this equation, what is the value of

b

0.155

1.155

15.5