Answer:
The magnitude of the work done by the snake against friction is 402 J.
Step-by-step explanation:
The work is given by:

Where:
F: is the force
d: is the distance
The distance traveled by the snake is given by the perimeter of the circle:

Now, the force in the direction of the movement is:
Finally, the work is:

Therefore, the magnitude of the work done by the snake against friction is 402 J.
I hope it helps you!