The greens want to put an addition on their house 18 months from now. they will need to save $10,620 in order to achieve this goal. they set aside the same amount each month, and after a year discover they have saved $6,120. the greens must adjust their plan in order to meet their goal, so they came up with the following options: option a: stay with saving the original amount each month but put the addition on one month later than originally planned. option b: increase the amount of money they save each month by $120 from their original plan. which of the following statements is true?