दी गई श्रृंखला में निम्नलिखित में से कौन सा अक्षर समूह प्रश्न चिह्न (?) को प्रतिस्थापित करेगा? YT, ?, AR, BQ, CP, DO

Which number will replace the question mark (?) in the following series? 83, 79, 71, 67, 59, 55, ?

Which of the following letter-number clusters will replace the question mark (?) in the given series to make it logically complete? HLE23, JJH21, LHK19, NFN17, ?