Table:
|  |  | 2019 |  | 2018 |
| --- | --- | --- | --- | --- |
|  | Amount | % of Revenues | Amount | % of Revenues |
| Comcast | $ 229 | 23% | $221 | 25% |
| Charter | 195 | 20% | 179 | 20% |
Paragraphs:
Description of Business
Key Clients. We work with the leading communication service providers located around the world. A partial list of our key clients as of December 31, 2019 is included below:
Clients that represented 10% or more of our revenues for 2019 and 2018 were as follows (in millions, except percentages):
See the Significant Client Relationships section of our Management’s Discussion and Analysis (“MD&A”) for additional information regarding our business relationships with these key clients.
Research and Development. Our clients around the world are facing competition from new entrants and at the same time, are deploying new services at a rapid pace and dramatically increasing the complexity of their business operations. Therefore, we continue to make meaningful investments in R&D to ensure that we stay ahead of our clients’ needs and advance our clients’ businesses as well as our own. We believe our value proposition is to provide solutions that help our clients ensure that each customer interaction is an opportunity to create value and deepen the business relationship.
Our total R&D expenses for 2019 and 2018 were $128.0 million and $124.0 million, respectively, or approximately 13% and 14%, respectively, of our total revenues. We anticipate the level of R&D investment in the near-term to be relatively consistent with that of 2019.
There are certain inherent risks associated with significant technological innovations. Some of these risks are described in this report in our Risk Factors section below.
Question:
What is the total revenue earned from Comcast in 2018 and 2019?
Answer: $(229 + 221)  = 450