Choose and Weekday Function

I am trying to create a CHOOSE and WEEKDAY Function.

I have successfully created the weekend column but I wasn't able to get the right function for weekday part.

What I want is to start the week every Monday. For example, any date from period April 21-25 should start April 21.

I attached the workbook Weekday for your reference. Thanks for the help!!!

Try:
=A2-MOD(WEEKDAY(A2,3),7)

Thank you so much, ragulduy!!! Can you please explain how does it work or the logic? Please bear with me I am just a newbie to excel formula and functions.

The Weekday function returns the weekday of a date (as you know), the second arguement, which I have set to 3, means that Tuesday will be a "1". The mod function returns the remainder if you divide the first number by the second, although now that I think about it, that bit is redundant. You can just use:
=A2-WEEKDAY(A2,3)