The function $c$ gives the partial length, in centimeters ($\text{cm}…

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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