Consider the following code snippet, where a voting service is accessed through two RPC calls:

 

is_vote_cast(voter_id): returns if the voter specified by the 'voter_id' has already cast her vote ('YES ' or 'NO)

cast_vote(cand_id, voter_id): casts the vote for the specified candidate by the specifier voter

voter_id = '243545'

cand_id = '90888'

if (proxy.is_vote_cast(voter_id) == 'NO') {

proxy.cast_vote(cand_id, voter_id)

}

Describe the ramification of three RPC call semantics: (i) Maybe, (ii) at-least-once, and (iii) at-most-once, on these two calls. Which semantic is best fit for which functions?