Table:
|  |  |  | Fiscal |
| --- | --- | --- | --- |
|  | Measure | 2019 | 2018 |
| Copper | Lb. | $ 2.93 | $  2.86 |
| Gold | Troy oz. | 1,309 | 1,281 |
| Silver | Troy oz. | 16.42 | 17.15 |
Paragraphs:
We use a wide variety of raw materials in the manufacture of our products. Cost of sales and gross margin are subject to variability in raw material prices which continue to fluctuate for many of the raw materials we use, including copper, gold, and silver. In fiscal 2019, we purchased approximately 172 million pounds of copper, 122,000 troy ounces of gold, and 2.6 million troy ounces of silver. The following table presents the average prices incurred related to copper, gold, and silver:
In fiscal 2020, we expect to purchase approximately 170 million pounds of copper, 120,000 troy ounces of gold, and 2.4 million troy ounces of silver.
Question:
What are the Cost of sales and gross margin are subject to?