Please show me how to use excel to work this problem Let X b

Please show me how to use excel to work this problem. Let X be normally distributed with mean u=120 and standard deviation o=20 . a. Find P(X 86) b. Find P(80 X 100)c. Find x such that P(X x) =0.40 d. Find x such that P(X > x) =0.90

Solution

Normal Distribution
Mean ( u ) =120
Standard Deviation ( sd )=20
Normal Distribution = Z= X- u / sd ~ N(0,1)                  
a)
P(X > 86) = (86-120)/20
= -34/20 = -1.7
= P ( Z >-1.7) From Standard Normal Table
= 0.9554                  
P(X < = 86) = (1 - P(X > 86)
= 1 - 0.9554 = 0.0446                  
b)
To find P(a < = Z < = b) = F(b) - F(a)
P(X < 80) = (80-120)/20
= -40/20 = -2
= P ( Z <-2) From Standard Normal Table
= 0.02275
P(X < 100) = (100-120)/20
= -20/20 = -1
= P ( Z <-1) From Standard Normal Table
= 0.15866
P(80 < X < 100) = 0.15866-0.02275 = 0.1359                  
c)
P ( Z < x ) = 0.4
Value of z to the cumulative probability of 0.4 from normal table is -0.253
P( x-u/s.d < x - 120/20 ) = 0.4
That is, ( x - 120/20 ) = -0.25
--> x = -0.25 * 20 + 120 = 114.94                  
d)
P ( Z > x ) = 0.9
Value of z to the cumulative probability of 0.9 from normal table is -1.28
P( x-u/ (s.d) > x - 120/20) = 0.9
That is, ( x - 120/20) = -1.28
--> x = -1.28 * 20+120 = 94.36