Fulton Enterprises sells three chemicals: petrol, septine and tridol. Petrol is the company's most profitable product (i.e., has the highest contribution margin ratio); tridol is the least profitable. Which one of the following events will definitely decrease the firm's overall breakeven point with regard to volume (i.e., decrease the number of combined units the firm needs to sell to breakeven) for the upcoming period? The purchase of new machinery and subsequent layoff of assembly workers An increase in the cost of petrol's raw materials A decrease in the selling price of tridol An increase in sales of petrol relative to the sales of septine and tridol