Given Are the First Three Terms of a Sequence That $m , m - 12 , m - 24$

Multiple Choice

Given are the first three terms of a sequence that is arithmetic. Find a1 and d.
- $m , m - 12 , m - 24$

A) $a _ { 1 } = m ; r = - 12$
B) $a _ { 1 } = m ; d = - 12$
C) $\mathrm { a } _ { 1 } = \mathrm { m } ; \mathrm { d } = \mathrm { m } - 12$
D) $\mathrm { a } _ { 1 } = \mathrm { m } ; \mathrm { d } = 12$