Total Costs in the Table Are A) Decreasing at a Constant Rate

Total costs in the table are:
$\begin{array}{|c|c|c|c|c|c|c|}\hline \begin{array}{c}\text { Control } \\\text { Variable }\end{array} & \begin{array}{c}\text { Total } \\\text { Benefits }\end{array} & \begin{array}{c}\text { Total } \\\text { Costs }\end{array} & \begin{array}{c}\text { Net } \\\text { Benefits }\end{array} & \begin{array}{c}\text { Marginal } \\\text { Benefit }\end{array} & \begin{array}{c}\text { Marginal } \\\text { Cost }\end{array} & \begin{array}{c}\text { Marginal } \\\text { Net Benefit }\end{array} \\\hline Q & B(Q) & C(Q) & N(Q) & \boldsymbol{M}(Q) & \boldsymbol{M}(Q) & M N B(Q) \\\hline 0 & 0 & 0 & 0 & -- & -- & -- \\\hline 1 & 900 & 100 & 800 & 900 & 100 & 800 \\\hline 2 & 1,700 & 300 & C & 800 & 200 & 600 \\\hline 3 & 2,400 & 600 & 1,800 & 700 & E & 400 \\\hline 4 & A & 1,000 & 2,000 & 600 & 400 & 200 \\\hline 5 & 3,500 & 1,500 & 2,000 & 500 & 500 & F \\\hline 6 & 3,900 & 2,100 & 1,800 & D & 600 & -200 \\\hline 7 & 4,200 & 2,800 & 1,400 & 300 & 700 & -400 \\\hline 8 & 4,400 & B & 800 & 200 & 800 & -600 \\\hline 9 & 4,500 & 4,500 & 0 & 100 & 900 & -800 \\\hline 10 & 4,500 & 5,500 & -1,000 & 0 & 1,000 & -1000 \\\hline\end{array}$

A) decreasing at a constant rate.
B) decreasing at a decreasing rate.
C) increasing at a constant rate.
D) increasing at an increasing rate.