Answer step it step by step

Assume that Zimbabwe and Portugal can switch between producing toothbrushes and producing hairbrushes at a constant rate. Machine Minutes Needed to Make 1 Toothbrush Hairbrush Zimbabwe 10 Portugal 5 6 1. Refer to Table 3-22. Zimbabwe and Portugal would not be able to gain from trade if Zimbabwe's opportunity cost of one toothbrush changed to a. 0 hairbrushes. b. 5/6 hairbrushes. c. 6/5 hairbrushes. d. Zimbabwe and Portugal can always gain from trade regardless of their opportunity costs