@Keyframes property ,showing an error

Tell us what’s happening:
Although the animation is working perfectly,but it is giving an error -The
@keyframes rule should use the animation-name of rainbow.I have used it
but still this test case is s showing error.It’s really frustrating.Please,help me.
This is the link for the lesson https://www.freecodecamp.org/learn/responsive-web-design/applied-visual-design/learn-how-the-css-keyframes-and-animation-properties-work



Your code so far


<style>
div {
  height: 40px;
  width: 70%;
  background: black;
  margin: 50px auto;
  border-radius: 5px;
}

#rect {
  animation-name: rainbow;
  animation-duration: 4s;

}

@Keyframes rainbow{
  0%{
    background-color:blue;
    }
  50%{
    background-color:green;
    }
  100%{
    background-color:yellow;
    }
}




</style>
<div id="rect"></div>

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User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.122 Safari/537.36.

Challenge: Learn How the CSS @keyframes and animation Properties Work

Link to the challenge:

It should be lowercase ‘k’.