'A' can complete a project in 15 days but worked only

There are 3 series, you have to find value of a, b, c and then establish relation among a,b,c.

19, 25, 45, a, 553, 2767

35           36           40           49           65           ?

22 15 10 20 33 93.5

299, 302, 308, 317, ?, 344

7, 8, 12, 21, 37, ?

1335       737         355         141         47           ?

? + (55)²= (140)²– (80)²– 6278

148, ‘?’ , 15 4 , 17 8 , 23 8 , 35 8 , 56 8

94           282         284         852         856         2562

123      125      129      132      ?      145