Plz help where I went wrong?

Tell us what’s happening:

Your code so far

<style type='text/scss'>
@mixin border-stroke($val) {
@if $val == light {
  border: 1px solid back;
@else if $val == medium {
  border: 3px solid black;
@else if $val == heavy {
  border: 6px solid black;
@else {
  border: none;

#box {
  width: 150px;
  height: 150px;
  background-color: red;
  @include border-stroke(medium);

<div id="box"></div>

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Challenge: Use @if and @else to Add Logic To Your Styles

Link to the challenge: