For the past decade, rubber powder has been used in asphalt cement to improve performance. The article "Experimental Study of Recycled Rubber-Filled High-Strength Concrete" (Magazine of Concrete Res., 2009: 549-556) includes a regression of y = axial strength (MPa) on x = cube strength (MPa) based on the following sample data:

a. Obtain the equation of the least squares line, and interpret its slope.
b. Calculate and interpret the coefficient of determination.
c. Calculate and interpret an estimate of the error standard deviation s in the simple linear regression model?

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x | 112.3 97.0 92.7 86.0 102.0 99.2 95.8 103.5 89.0 86.7 y75.0 71.0 57.7 48.7 74.3 73.3 68.0 59.3 57.8 48.5