How to Change textbox on combobox selection while adding table rows

How to Change textbox on combobox selection while adding table rows

I have a table that adds rows dynamically it has a selection box that changes the value of a textbox when the onchange function is fired but the problem is that it resets all the textboxes instead of that particular empty one.

Please see the fiddle below thanks

https://jsfiddle.net/josephat/xd7zknyc/3/