**Given data:**
- Weight of the body (W) = 20 N
- Angle of inclination (θ) = 20 degrees
- Initial velocity (u) = 12 m/s
- Coefficient of friction (μ) = 0.15

**a) Maximum distance moved up the inclined plane:**

To find the maximum distance that the body will move up the inclined plane, we need to determine when the body comes to rest.

1. Resolve the weight of the body into two components:
- Perpendicular component (W⊥) = W * cosθ
- Parallel component (W∥) = W * sinθ

2. Calculate the normal force (N) acting on the body:
N = W⊥ = W * cosθ

3. Determine the frictional force (f) acting on the body:
f = μN = μ * W * cosθ

4. Calculate the net force acting on the body along the inclined plane:
Net force = W∥ - f

5. Equate the net force to zero to find when the body comes to rest:
W∥ - f = 0

6. Substitute the values of W∥ and f:
W * sinθ - μ * W * cosθ = 0

7. Simplify the equation:
sinθ = μ * cosθ

8. Substitute the values of sinθ and cosθ:
sin20 = 0.15 * cos20

9. Solve for cos20:
cos20 = sin20 / 0.15

10. Substitute the value of cos20 back into the equation to find sin20:
sin20 = 0.15 * (sin20 / 0.15)

11. Solve for sin20:
sin20 = sin20

12. This equation is valid for all values of sin20.

Therefore, the body will never come to rest and will continue to move up the inclined plane indefinitely. Hence, the maximum distance moved up the inclined plane is infinite.

**b) Velocity when the body returns to its original position:**

Since the body does not come to rest and continues to move up the inclined plane indefinitely, it will not return to its original position. Therefore, the velocity when the body returns to its original position cannot be determined.

Explanation: The given problem involves the motion of a body on an inclined plane. To solve for the maximum distance moved up the inclined plane, we need to determine when the body comes to rest. By resolving the weight of the body into two components, calculating the normal force and frictional force, and equating the net force to zero, we can find the condition for the body to come to rest. However, in this problem, the body will never come to rest and will continue to move up the inclined plane indefinitely. Hence, the maximum distance moved up the inclined plane is infinite. Similarly, since the body does not come to rest and continues to move up the inclined plane indefinitely, it will not return to its original position. Therefore, the velocity when the body returns to its original position cannot be determined.