Express the Sum Using Summation Notation $$a + a r + a r ^ { 2 } + \ldots + a r ^ { 13 }$$

Multiple Choice

Express the sum using summation notation. Use 1 as the lower limit of summation and i for the index of summation.
- $$a + a r + a r ^ { 2 } + \ldots + a r ^ { 13 }$$

A) $\sum _ { i = 1 } ^ { 14 } a r ^ { i - 1}$
B) $\sum _ { \mathrm { i } = 1 } ^ { 13 } a r ^ { \mathrm { i } }$
C) $\sum _ { i = 1 } ^ { 13 } ( a r ) ^ { i }$
D) $\sum _ { i = 1 } ^ { 13 } ( \operatorname { ar } ) ^ { i - 1 }$