Question: Is there a value that when passed to a proc with default parameter value forces the use of the default?

I tried inserting contents of my worksheet here but for some reason procedure test2 does not appear. Therefore, here is a screenshot.

What I would like is for the call r() above to print out 3,2 and then 5.

Basically, I'd like to know how I can call a function that has default parameter values with a value that makes the function use the default parameter value.

In the code above, the variable r is assigned to the return value of test2, which is the function called "inner". The function inner accepts an argument "b" and calls the function "test" passing in this "b" as the second argument. If I don't pass any argument to "inner" then it defaults to Null, which then gets passed to "test".

I want this Null to force "test" to use its default value for parameter "b".

PS As an extra, why does it give a "not able to parse" error when we declare a local inside of a proc as above? Note that I have it commented out. 

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