import math

mu = 20
sigma = 2

x_1 = 19.5 

x_2_a = 20
x_2_b = 22

# P(X <= x) = 0.5 * (1+math.erf((x - mu)/(sigma * 2**0.5)))
p_less_than_19_5 = 0.5 * (1+math.erf((x_1 - mu)/(sigma * 2**0.5)))

print(round(p_less_than_19_5,3))

# (a <= X <= b) = F(b) - F(a)
p_between_20_and_22 = 0.5 * (1+math.erf((x_2_b - mu)/(sigma * 2**0.5))) - 0.5 * (1+math.erf((x_2_a - mu)/(sigma * 2**0.5)))

print(round(p_between_20_and_22, 3))