$($c$)$ Let the following Haskell program be given

main :: IO $()$

main $=$ getLine $>>=$ mainLoop

where mainLoop previousInput $=$ do

$\{$

putStrLn $($previousInput $++"!")$;

i $<-$ getLine;

if i $/=$ previousInput then

mainLoop i

else

return $()$

$\}$

$($i$)$ Explain informally how this code works. Under which condition will this

program terminate?

$($ii$)$ Give the output assuming that the user enters successively Hi

Program $??($where each

corresponds to hitting the return$/$enter key$).$

$($iii$)$ What is the type of the subexpression mainLoop?

$[5$ marks$]$

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