1. **State the problem:** We need to calculate the four-firm concentration ratio (CR-4) for the given market. The CR-4 measures the market share of the top four firms combined. 2. **Formula:** The four-firm concentration ratio is given by: $$\text{CR-4} = \frac{\text{Sum of sales of top 4 firms}}{\text{Total market sales}} \times 100\%$$ 3. **Identify the top 4 firms by sales:** - Dap: 7.4 million - American Jaybird: 7.1 million - Expressive: 6.8 million - LA & Company: 6.2 million 4. **Calculate total sales of top 4 firms:** $$7.4 + 7.1 + 6.8 + 6.2 = 27.5 \text{ million}$$ 5. **Calculate total market sales:** Sum all firms' sales: $$7.4 + 7.1 + 6.8 + 6.2 + 5.3 + 4.2 = 36.99999999999999 \approx 37.0 \text{ million}$$ 6. **Calculate CR-4:** $$\text{CR-4} = \frac{27.5}{37.0} \times 100\% = 74.324\% \approx 74\%$$ 7. **Interpretation:** The top four firms control approximately 74% of the market sales. **Final answer:** The four-firm concentration ratio is **74%**.