The mean of a normal probability distribution is 500 and the standard deviation is 25. About 68% of the observations lie between what two values? 350 and 650

480 and 520

475 and 525

400 and 600

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