Table 13 Shows the Hypothetical Trade-Off Between Different Combinations of Brushes

Table 1.3 shows the hypothetical trade-off between different combinations of brushes and combs that might be produced in a year with the limited capacity for Country X, ceteris paribus.Complete the table by calculating the required opportunity costs for brushes and combs.
$\begin{array}{|c|c|c|c|c|c|}\hline & \begin{array}{c}\text { Number } \\\text { of } \\\text { Brushes }\end{array} & \begin{array}{c}\text { Opportunity Cost } \\\text { of Brushes in } \\\text { Terms } \\\text { of Combs }\end{array} & \begin{array}{c}\text { Number } \\\text { of Combs }\end{array} & \begin{array}{c}\text { Opportunity Cost } \\\text { of Combs in Terms } \\\text { of Brushes }\end{array} \\\hline \mathrm{J} & 0 & & 4 & \\\hline \mathrm{K} & 10 & & 3 & \\\hline \mathrm{L} & 17 & & 2 & \\\hline \mathrm{M} & 21 & & 1 & \\\hline \mathrm{N} & 23 & & 0 & \\\hline\end{array}$

$\text {Table \(1.3\) }$
$\text {Production Possibilities for Brushes and Combs}$
On the basis of your calculations in Table 1.3, in the production range of 21 to 23 brushes the opportunity cost of producing one more comb in terms of brushes is

A) 1/21.
B) 21/23.
C) 1/2.
D) 4.