निम्नलिखित अल्फ़ान्यूमेरिक श्रृंखला में लुप्त पद ज्ञात कीजिए: W-144, ?, S-100, Q-81, O-64

What should come in place of '?' in the given number series? 111, 110, 106, 97, 81, ?

Which of the given letter-number clusters will replace the question mark (?) in the following series to make it logically complete? NVA 7, KSX 14, HPU 21, EMR 28, ?