Treat \( Y = 10 + 0.6X \) as a function and differentiate it with respect to \( X \): \[ \frac{dY}{dX} = 0.6 \] By definition, the marginal physical product (MPP) of an input is exactly this derivative, the rate of change of output per additional unit of input, so the coefficient 0.6 is the MPP. Since the function is linear, this same derivative is also, by definition, the slope of the line when \( Y \) is plotted against \( X \). Elasticity of production, in contrast, equals \( \frac{dY}{dX}\cdot\frac{X}{Y} \), a ratio that changes with \( X \) and \( Y \) and is not simply 0.6; average physical product (APP) equals \( \frac{Y}{X} = \frac{10}{X}+0.6 \), which likewise varies with \( X \). So only MPP and Slope match the constant coefficient 0.6, confirming (A) and (B) only, option (4).