Statistics help! Standard Deviation and mean word problem.

This problem probably isn't very hard, but how to set it up is confusing me a little.. Could you please help me out with this problem by showing all the steps? Thanks so much!

Weights of adult green sea urchins are normally distributed with mean 52.0 g and a standard deviation 17.2 g.

a) Find the percentage of adult green sea urchins with weights between 50 g and 60 g.

b) Obtain the percentage of adult green sea urchins with weights above 40 g.

Anything helps!

Let X be weights of adult green sea urchins.

X ∼ n(52; 17.2)

a)

P(50 ≤ X ≤ 60) = P((50 - 52)/17.2 ≤ (X - 52)/17.2 ≤ (60 - 52)/17.2) = P( - 0.12 ≤ Z ≤ 0.47) =

P(Z ≤ 0.47) - P(Z ≤ - 0.12) = 0.6808 - 0.4207 = 0.2601

b)

P(X ≥ 40) = P((X - 52)/17.2 ≥ (40 - 52)/17.2) = P(Z ≥ - 0.7) = 0.758

Standardized Normal Distribution.