Question 1180520
The difference between those two values is 13.89.
The height of the rectangle is 1/52 or 0.0192, the probability of a birth in a specific week.
The base is from 26.1 to 39.99
The area of that is the product of 13.89 (1/52)=0.2671
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Rough check--from 26 to 39 weeks is 1/4 of the time or probability 0.25
from 26 to 40 weeks is 14/52 or probability 0.2692.