During autumn months, passenger railroads across the globe deal with a condition called slippery rail. It results from a combination of water, leaf oil, and pressure from the train’s weight, which creates a slippery black ooze that prevents trains from gaining traction.
One solution for slippery rail is to cut back trees from all of a rail firm’s rail network on a regular basis, thereby helping prevent the problem from developing. If incurred, would this railroad expense be a better example of a fixed cost or a variable cost? Why?

It is an example of a fixed cost because the cost doesn't vary with the number of trains.

Explanation:

One solution for slippery rail is to cut back trees from all of a rail firm’s rail network on a regular basis, thereby helping prevent the problem from developing. If incurred, would this railroad expense be a better example of a fixed cost or a variable cost? Why?

This is an example of a fixed cost because the cost doesn't vary with the number of trains.

The expanse of cutting a tree would be regarded as fixed costs considering that it is not related with the rail service provide.Fixed cost does not affect on the further expansion of output, thus, the cost incurred on cutting tree for preventing problem concerned with the rail track is considered as a fixed cost

is there a year set? the question is incomplete