Calculate the area of the square base.

The base is a square with side length $8 \text{ cm}$.

$$\text{Base Area} = \text{side} \times \text{side} = 8 \text{ cm} \times 8 \text{ cm} = 64 \text{ cm}^2$$

The height of the pyramid is $10 \text{ cm}$.

$$\text{Volume} = \frac{1}{3} \times \text{Base Area} \times \text{height}$$ $$\text{Volume} = \frac{1}{3} \times 64 \text{ cm}^2 \times 10 \text{ cm}$$ $$\text{Volume} = \frac{640}{3} \text{ cm}^3 \approx 213.33 \text{ cm}^3$$

The volume of pyramid (a) is $\boxed{\text{213.33 cm}^3}$.

The base is a rectangle with length $8 \text{ cm}$ and width $6 \text{ cm}$.

$$\text{Base Area} = \text{length} \times \text{width} = 8 \text{ cm} \times 6 \text{ cm} = 48 \text{ cm}^2$$

The height of the pyramid is $6 \text{ cm}$.

$$\text{Volume} = \frac{1}{3} \times \text{Base Area} \times \text{height}$$ $$\text{Volume} = \frac{1}{3} \times 48 \text{ cm}^2 \times 6 \text{ cm}$$ $$\text{Volume} = 16 \text{ cm}^2 \times 6 \text{ cm} = 96 \text{ cm}^3$$

The volume of pyramid (b) is $\boxed{\text{96 cm}^3}$.

The base is a right-angled triangle with base $4 \text{ cm}$ and height $6 \text{ cm}$.

$$\text{Base Area} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 4 \text{ cm} \times 6 \text{ cm} = 12 \text{ cm}^2$$

The height of the pyramid is $5 \text{ cm}$.

$$\text{Volume} = \frac{1}{3} \times \text{Base Area} \times \text{height}$$ $$\text{Volume} = \frac{1}{3} \times 12 \text{ cm}^2 \times 5 \text{ cm}$$ $$\text{Volume} = 4 \text{ cm}^2 \times 5 \text{ cm} = 20 \text{ cm}^3$$

The volume of pyramid (c) is $\boxed{\text{20 cm}^3}$.