Reorder column layout in mobile view

I’m using a two column layout. Lets call the left column A and the right column B. Thus the column layout in desktop view is as follows:

Column A | Column B

and in mobile view, the column layout will be:

Column A
Column B

ie Column A is on top of Column B

How can I retain the current desktop view but in mobile view have column B on top of column A. So it looks like this:

Column B
Column A

A solution would be much appreciated

With thanks

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