The normal distribution of the grades in the class is between 72 and 14.

The bottom 10% obtained a F of P(ZF)=0.10.

The remaining 20% obtained a D of P(FZD)=0.20.

Following that, 40% obtained a C with a P(DZC) value of 0.40.

The remaining 20% received a B with a P(CZB) value of 0.20.

Finally, the top 10% received A, which equals P(Z>B)=0.10.

I determined the cutoff value for C as P(ZC)=0.70 using the z score table and obtain C=0.5244

So;

When Z equals 0.5244, X equals 0.5244.

I used the following formula to determine the cutoff grades:

X=(Z)+

=(0.524414)+72

=79.341679

As a result, the cutoff grade for B's and C's is 79.

response-I am not understanding the notation FZD, etc, can you help? How did you get the .70 and what does that represent? You have "When Z equals 0.5244, X equals 0.5244."...this is not correct...why?