Find a Formula for The $n t h$ Term of the Following Geometric Sequence, Then Find the 4

Multiple Choice

Find a formula for the $n t h$ term of the following geometric sequence, then find the 4 th term of the sequence.
$7,28,112 , \ldots$

A) $a _ { n } = 7 ( 4 ) ^ { n } ; a _ { 4 } = 448$
B) $a _ { n } = 7 ( 4 ) ^ { n } ; a _ { 4 } = 1792$
C) $a _ { n } = 7 ( 4 ) ^ { n - 1 } ; a _ { 4 } = 1792$
D) $a _ { n } = 7 ( 4 ) ^ { n - 1 } ; a _ { 4 } = 448$
E) $a _ { n } = 7 ( 4 ) ^ { n - 1 } ; a _ { 4 } = 112$