Could someone explain to me why i got this wrong? i'm assuming its because the answer included 1 so it could've possibly been considered infinite? i honestly doesn't know what it means though when it refers to none or infinite.

When george started his current job, his employer told him that at the end of the first year, he would receive two vacation days. after each year worked, his number of vacation days will double up to five work weeks (25days) of payed vacation. how many vacation days will he have in 4 years