A "check", the form most routine maintenance (on aircraft) takes, comes is several grades, referred to as "letter checks" A through D; all performed at regular intervals. Which of the following four hour intervals, representing A, B, C, and D are correct?
125; 750; 5,000; 20,000
100; 500; 5,000; 25,000
125; 750; 3,000; 20,000
100; 500; 3,000; 25,000
