Tendons are, essentially, elastic cords stretched between two fixed ends. $$As $$such$,$ they can support standing waves. A woman has a $18$ cmcm $-$long Achilles tendon$-$connecting the heel to a muscle in the calf $-$ with a cross $-$ section area of $86$ mm$2$mm$2.$ The density of tendon tissue is $1100$ kg$/$m$3$kg$/$m$3.$

Part A

For a reasonable tension of $570$ NN $,$ what will be the fundamental frequency of her Achilles tendon?

Express your answer with the appropriate units.