According to the study by Centers for Disease Control, average level of lead in children's blood in United States can be modeled by function.
L(t) = 18(o.88)^t,
where t is number of years since 1976, first year data are available, and L(t) is average blood lead level, measured in micrograms per deciliter.
Find annual decay factor and rate and graph the function L over interval 0