Find the selling price if: 1. Cost price = 10 000, Profit = 20% 2. Cost price = 2 400, Loss = 30% 3. Cost price = 600, Loss = 10% 4. Cost price = 4 000, Profit = 10%

Since there is a profit of $20\%$, the selling price is $100\% + 20\% = 120\%$ of the cost price.

The selling price is $\boxed{\text{N}12\,000}$.

2)

Since there is a loss of $30\%$, the selling price is $100\% - 30\% = 70\%$ of the cost price.

The selling price is $\boxed{\text{N}1\,680}$.

3)

Since there is a loss of $10\%$, the selling price is $100\% - 10\% = 90\%$ of the cost price.

The selling price is $\boxed{\text{N}540}$.

4)

Since there is a profit of $10\%$, the selling price is $100\% + 10\% = 110\%$ of the cost price.

The selling price is $\boxed{\text{N}4\,400}$.