If ∑ = {a, b, d, e, f } then number of strings in ∑ of length 4 such that no symbol is used more than once in a string is

If ∑ = {a, b, d, e, f } then number of strings in ∑ of length 4 su

1.	If ∑ = {a, b, d, e, f } then number of strings in ∑ of length 4 such that no symbol is used more than once in a string is
A.	360
B.	35
C.	320
D.	49
Answer» B. 35