Fill in the blank space for the given series with the correct alternative.
$3, 10, 20, 33, 49, 68, (\ldots)$

To answer these questions, study the following arrangement of digits, letters and symbols carefully.

$6, N, P, =, @, 7, 1, \&, R, T, 3, L, B, \star, E, 4, \#, 8, G, H, \$, 5, K, M, ?, 2, D, C$

'$= N$' is to '$T 1$' and '$B 3$' is to '$G 4$' in the same way as '$EB$' is to

These questions are based on the following arrangement. Study it carefully and answer the questions.

$8 ,H ,\% ,3,7 ,T,A ,4 ,\# ,6 ,B,I ,@ ,R ,1 ,Q ,\star, L,E ,2 ,K ,\$ ,U ,5,9$

How many such symbols are in the above arrangement each of which is immediately followed by a number but not immediately preceded by another number?