The properties of Cu as a function of % CW are given by the following equations: Yield Stress (Ksi) = -0.005X2 + 1.1X+ 2

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The properties of Cu as a function of % CW are given by the
following equations:
Yield Stress (Ksi) = -0.005X2 + 1.1X+ 23.4,
% elongation = 0.005X2 - 0.7X + 30.8,
where X is the % of CW.
Given the above, estimate the % elongation when rolling a Cu
plate from its annealed state, from an initial thickness of 9 mm to
2 mm in a single pass.
Write your result with a decimal.