Explanation:
The railroad felt that the demand for passenger service was inelastic and opponents of the rate increase felt it was inelastic.
Inelastic demand is used in economics to give the idea that consumers buy or use same amount of the product irrespective of the increase or decrease in the price of the product.
So in this situation, the opponent wanted to say that same number of people will travel by rail no matter if the price of the tickets will increase or decrease. The passenger service will be inelastic.
So the answer is "the railroad felt that the demand for passenger service was inelastic and opponents of the rate increase felt it was inelastic".