10 11 15 24 40 6 (a) (b) (c) (d) (e) What will come in place of (c)?

As per the details in the question the series is in the form of
First series :-
First term = 10
Second term = First term + 1²
⇒ Second term = 10 + 1² = 10 + 1 = 11
Third term = Second term + 2²
⇒ Third term = 11 + 2² = 11 + 4 = 15
similarly , we can find the all others terms .
Second series :-
First term = 6
Second term = First term + 1²
⇒ Second term = 6 + 1² = 6 + 1 = 7
Third term = Second term + 2²
⇒ Third term = 7 + 2² = 7 + 4 = 11
Fourth term = Third term + 3²
⇒ Fourth term = 11 + 3² = 11 + 9 = 20
Hence , the place value of ( c ) is 20 .