Table:
| Fiscal Years |  |  |  |
| --- | --- | --- | --- |
|  | 2019 | 2018 | 2017 |
| Statements of Operations: |  |  |  |
| Revenue | 100% | 100% | 100% |
| Cost of revenue | 43% | 50% | 55% |
| Gross profit | 57% | 50% | 45% |
| Operating expenses: |  |  |  |
| Research and development | 120% | 79% | 79% |
| Selling, general and administrative | 86% | 79% | 81% |
| Loss from operations | (149)% | (108)% | (115)% |
| Interest expense | (3)% | (1)% | (1)% |
| Interest income and other expense, net | 2% | 1% | —% |
| Loss before income taxes | (150)% | (108)% | (116)% |
| Provision for income taxes | 1% | 1% | 1% |
| Net loss | (151)% | (109)% | (117)% |
Paragraphs:
Results of Operations
The following table sets forth the percentage of revenue for certain items in our statements of operations for the periods indicated:
Impact of inflation and product price changes on our revenue and on income was immaterial in 2019, 2018 and 2017.
Question:
What is the total proportion of cost of revenue as a percentage of revenue in 2017 and 2018?
Answer: (55 + 50)  = 105