In order to save money, some of Company X's manufacturing

In order to save money, some of Company X's manufacturing plants converted from oil fuel to natural gas last year, when the cost of oil was more than the cost of natural gas. Because of a sudden, unexpected shortage, however, natural gas now costs more than oil, the price of which has fallen steeply over the past year. The cost of conversion back to oil would more than negate any cost savings in fuel. So Company X's fuel costs this year will be significantly higher than they were last year.

Which of the following is an assumption on which the argument above depends?

1. Company X does not have money set aside for the increased costs of fuel.

OOS

2. The increase in the cost of fuel cannot be offset by reductions in other operating expenses.

OOS

3. The price of natural gas will never again fall below that of oil.

"Will never" is out of scope. We only need a comparision for this year vs last year.

4. The cost of fuel needed by those of Company X's plants that converted to natural gas is not less than the cost of fuel needed by those plants still using oil.

This is the right assumption. As we know that only some of the oil plants have converted to gas, there are still plants running with oil, so in order for the fuel costs to significantly increase we are assuming that the price hike by gas is not offset by the drop in prices of oil.

5. The price of oil will not experience a sudden and steep increase.

It does not matter if the price of oil increases as this only confirms that the fuel costs, which have already been hiked with conversion to natural gas are going to further increase