Identify the 16th term of a geometric sequence where a1 = 4 and a8 = -8,748

Identify the 16th term of a geometric sequence where a1 = 4 and a8 = -8,748… .

a. -172,186,884.
b. -57,395,628.
c. 57,395,628.
d. 172,186,884.