First let us calculate for the z score using the formula:
z = (x – u) / s
where u is the mean height of men = 69 in, x is the height of the door = 76, and s is the standard deviation = 2.8 in
z = (76 – 69) / 2.8
z = 2.5
From the standard probability table, at z = -2.5 the probability P is:
P = 0.9938 = 99.38%