Production Function -What Is the APP of Using 1 Unit of Input

Production Function.
Below is the production function for an agribusiness firm, where X is the input, and Y is the output.
$\begin{array}{llll}\underline{\mathrm{X}} & \underline{\mathrm{Y}} & \underline{\text { APP }} & \underline{\mathrm{MPP}} \\0 & \underline {\quad} & -- & -- \\1 & 10 & \underline {\quad} & 10 \\2 &\underline {\quad} & 15& \underline {\quad} \\3 & 45& \underline {\quad} & 15 \\4 & 50 &\underline {\quad} & \underline {\quad} \\5 & 45 &\underline {\quad} & \underline {\quad} \\6&\underline {\quad} &6&-9\end{array}$
-What is the APP of using 1 unit of input?

A) 0
B) 10
C) -10
D) 1