A certain calling card gives you the following rate to call Malaysia. There is a connection fee of $0.39 which allows you to connect for up to (but not including) one minute. For each additional minute or part of a minute, there is a $0.24 cent charge. (For example, 1 minute up to but not including 2 minutes costs $0.63.) This fare is only valid for up to (but not including) 40 minutes. 

Express this information as a function, where f(x) represents the amount of money charged and x represents the number of minutes which have elapsed.