The following graph is the production possibilities curve of a nation. A graph plots drill presses versus bread. The graph is a concave downward curve.The horizontal axis is labeled bread. It ranges from 0 to 4 in increments of 1. The vertical axis is labeled drill presses. It ranges from 0 to 10 in increments of 2. The graph is a concave downward curve that begins at A (0, 10) and falls with increasing steepness through B (1, 9), C (2, 7), D (3, 4) and ends at E (6, 0). The total opportunity cost of 10 drill presses is