The function \(c\) gives the partial length, in centimeters (cm), of …

The function

c

gives the partial length, in centimeters (cm), of the circumference of a circle with a radius that measures

r

cm. According to the function, for each increase of 18 cm in the length of the radius, this partial length of the circumference increases by

k π

cm. What is the value of

k

72/5

14.4

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