Select the letter-pair that can replace the question

89     78     74     67     63    ?

Which of the following numbers will replace the question mark (?) in the given series?

69, 70, 74, 83, ?, 124

32 63 121 ? 453 889

The number of terms in the sequence 5, 20, 80, 320,……………., 5120 is:

620 632 608 644 596 ?

6              16           116         566         2272       6814

6000 3002 1503 ? 378.75 191.375 97.6875

Select the number from among the given options that can replace the question mark (?) in the following series.

8, 27, 64, 125, 216, ?

84, 61, 80, 57, 76, ?