Find all elements of symmetry and the point group of the quarternary ammonium ion shown here. Is it chiral or achiral?

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symmetry elements:    01 2 3  C2    01 2 3  C3    01 2 3  C4    01 2 3  C5    01 2 3  C6    01 2 3  C    01  i    01 2 3  S4    01 2 3  S6    01 2 3  S8    01 2 3

point group:  C2  C2v  C4  C4h  Cs  Ci  D2  D2d  D2h  D2v  S4  S8  other

chirality:  chiral  achiral