math 30 help

Question 7 Not yet answered Points out of 1 Flag question The function A = Age 0.0099* models the amount in pounds of a particular radioactive material stored in a concrete vault, where x is the number of years since the material was put into the vault How many years will it be until 30% of the original amount remains in the vault? Round off to the nearest year. Select one: A. 30 years OB. 36 years OC. 74 years OD. 122 years OE. None of the above