Cryptarithmatic

Given the shown expression, Find the value of each letter given the following:

Each letter should have a unique and distinct value

Each letter represents only one$-$digit throughout the problem

Numbers must not begin with zero i$.$e$.,0937($wrong$),937$

$\backslash$table$[[$TWO$],[+,$ TWO$],[$FOUR$]]$

$($correct$).$

$4.$ After replacing letters by their digits, the resulting arithmetic operations must be correct

We can use Constraint Satisfaction Problem $($CSP$)$ to solve the Cryptarithmatic puzzle. Answer the following question.

What are the variables?

And these questions also,

$4.$ Is O$=2$ a valid assignment? Why?

$5.$ List ALL the constraints in the expression?

$6.$ Use AC$3$ methodology to update the domain of each variable according to the constraints you found.