a. Find the z value of this, round to two decimal places.

b. Add areas of z values provided by a and d.

Same with c

d. Standard deviation = 78/sqrt of 50

(80-78)/(78/sqrt of 50)=z value,

Then use the table to find the corresponding value.

Sorry I have an emergency right now. You can ask me any questions you like about this, I have to submit this now or else I will be in bad situation, I hope you understand, thanks.