3 - C# functions

I am a beginner C# developer. I need help someone to write 3 functions:

private int minsToWeekly(DateTime currentTime){
//returns the number of minutes between currentTime and this Friday at 4PM local computer time
}

private int minsToThirdFriday(DateTime currentTime){
//returns the number of minutes between currentTime and the next occuring third Friday of the month at 4PM local computer time
}

private int minsToThirdFridayOfNextMonth(DateTime currentTime){
//returns the number of minutes between currentTime and the second occuring third Friday of the month at 4PM local computer time
}