Multi Level Dependable Dropdown and Text Field

Hi! Experts, 

I am creating a PDF Fillable Form. I created a Dependable Dropdown it's working using the below code 

First Dropdown Name: "Tile"

Second Dropdown Name: "Condition"

This code is pasted in First Dropdown "Tile"

var f = this.getField("Condition");
switch(event.value){

case "Terracotta":
f.setItems(["lichen"]);
break;

case "Concrete Tiles":
f.setItems(["Acceptable","Fair","Poor","Mould","Moss" ]);
break;

case"-Select-":
f.clearItems();}

its create dropdown items in 2nd dropdown. 

NOW I want to auto-populate the Description based on 2nd dropdown selected in 

Third Field Name: "Description"

For Exemple:

in 2nd dropdown "Acceptable" Selected it auto populate description in "Description" field and so on. 

Kindly Help me out.