Hens usually begin laying eggs when they are about 6 months

Hens usually begin laying eggs when they are about 6 months old. Young hens tend to lay smaller eggs, often weighing less than the desired minimum weight of 53grams. By the time these hens have reached the age of one year, the eggs they produce average 66.5 grams, and 98% of them are above the minimum weight. What is the standard deviation for these older hens?

P(X > 53) = 98%

P( Z > 53 - 66.5 / sd) = 98%