Question

Which of the following series is equal to 10,920?
A:Summation symbol^8 *0.5 *4^k-1
k=3
B: Summation symbol^8 *0.5 *4^k-1
K=2
C:Summation symbol^8 *0.5 *4^k-1
K=3
D: Summation symbol^7 *0.5 *4^k-1
K-3