How to calculate AVERAGE FIXED COST, AVERAGE SEMI-FIXED COST, AVERAGE VARIABLE COST, AVERAGE MIXED COST??

Can you simplify 4/7? 24 points will be awarded!

The first-serve percentage of a tennis player in a match is normally distributed with a standard deviation of 4.3%. if a sample of 15 random matches of the player is taken, the mean first-serve percentage is found to be 26.4%. what is the margin of error of the sample mean? a. 0.086% b. 0.533% c. 1.11% d. 2.22%

According to the general equation for conditional probability if p(anb)=3/7 and p(b)=7/8 what is p(a i b)