diff --git a/5981ff1daf72e8747d000091/index.js b/5981ff1daf72e8747d000091/index.js
new file mode 100644
index 0000000..2f56c21
--- /dev/null
+++ b/5981ff1daf72e8747d000091/index.js
@@ -0,0 +1,22 @@
+
+class Potion {
+  constructor(color, volume) {
+    this.color = color;
+    this.volume = volume;
+  }
+  mix(that) {
+    const volume = this.volume+that.volume;
+    const color = [];
+    for (let i = 0; i < this.color.length; ++i) {
+      const a = this.color[i] * this.volume;
+      const b = that.color[i] * that.volume;
+      color[i] = Math.ceil((a + b) / volume);
+    }
+    return new Potion(color, volume);
+  }
+}
+
+const p1 = new Potion([255, 255, 255],  7);
+const p2 = new Potion([ 51, 102,  51], 12);
+
+p1.mix(p2);