You run a program that implements the following pseudocode $($where arrow $$ means assignment$)$

and is written using some programming language:

a $5$

b a

a $6$

Initialize c to the current date $($today$)$ object

Initialize e to the previous date $($yesterday$)$ object

d c

Update the state of object c to the next date $($tomorrow$)$

e d

After that, you evaluate all variables $($dereferencing whenever necessary$)$ and find that a evaluates to $6,$ b evaluates to $5,$

c$,$ d$,$ and e evaluate to the next date $($tomorrow$)$ object. Which model for variables does this programming language use?

Select the best answer:

$($a$)$ Reference model for variables

$($b$)$ Value model for variables

$($c$)$ Mixed model for variables

$($d$)$ Dynamic model for variables

$($e$)$ None of the above