4300 BC to the Vail to Servants of the Middle Ages—Tipping's simple basis: u(t, s) = −[n(s) − t]2 + f(t, s) − t https://www.quora.com/What-is-the-origin-of-tipping-gratuity/answer/Brian-Roemmele?srid=Pi3&share=f628af0f …
8:36 PM - 23 Dec 2015
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