The mean student degree of electronic division in probability and statistics subject of 66 students is 77% and the standard deviation is 10 degrees. Assuming the degrees are normally distributed, find...

Extracted text: The mean student degree of electronic division in probability and statistics subject of 66 students is 77% and the standard deviation is 10 degrees. Assuming the degrees are normally distributed, find how many students' degree (a) between 60 and 80 degrees, (b) more than 85 degrees, and (c) less than 50 degrees? Note: for avoided the zero probability take +0.5 degree