K$-$Anonymity

You are given a database where individuals are listed by $7-$digit phone numbers. Assume that each phone number is unique. You are trying to anonymize the database by replacing the phone number with an alternative ID$.$ Which degree of K$-$anonymity do you achieve for the following ID choices? Explain your solutions!

a$)$ ID $=$ Is$\_$Even$($phone$\_$number$)?$

b$)$ ID $=($Does phone$\_$number end in $0,1,2,3,4$ or $5)?$

c$)$ ID $=1$st three digits of phone$\_$number

d$)$ ID $=$ sum of first two digits of phone number