Consider the Following Production and Cost Schedule for a Firm

Consider the following production and cost schedule for a firm. $$\begin{array}{l}\begin{array} { | l | l | l | l | } \hline \begin{array} { l } \text { Total Number of } \\\text { Units of the } \\\text { Factor }\end{array} & \begin{array} { l } \text { Total Number of } \\\text { Units of Output }\end{array} & \begin{array} { l } \text { Price per Unit } \\\text { of Output }\end{array} & \begin{array} { l } \text { Total Cost } \\\text { of Production }\end{array} \\\hline 10 & 30 & \$ 10 & \$ 100 \\\hline 11 & 44 & \$ 10 & \$ 110 \\\hline 12 & 64 & \$ 10 & \$ 120 \\\hline 13 & 78 & \$ 10 & \$ 130 \\\hline 14 & 84 & \$ 10 & \$ 140 \\\hline 15 & 86 & \$ 10 & \$ 150 \\\hline\end{array}\\\text { TABLE 13- } 1\end{array}$$
-Refer to Table 13- 1. Diminishing marginal returns begins to set in with the unit of the factor of production.

A) 13th
B) 10th
C) 12th
D) 11th
E) 14th