Table 103 Hotspur Incorporated, a Manufacturer of Microwave Ovens, Is a Price

Table 10.3
$$\begin{array} { | c | c | } \hline \begin{array} { c } \text { Number of } \\\text { Workers }\end{array} & \begin{array} { c } \text { Output of Microwave } \\\text { Ovens per Week }\end{array} \\\hline 1 & 30 \\\hline 2 & 55 \\\hline 3 & 75 \\\hline 4 & 90 \\\hline 5 & 100 \\\hline 6 & 105 \\\hline\end{array}$$ Hotspur Incorporated, a manufacturer of microwave ovens, is a price taker in its input and output markets. The firm hires labour at a constant wage rate of $800 per week and sells microwave ovens at a constant price of $80. Table 10.3 shows the relationship between the quantity of labour it hires and the quantity of microwave ovens it produces.
-Refer to Table 10.3.The amount of profit added as a result of hiring a fourth worker is _________.

A) $7200
B) $1200
C) $800
D) $400