A pharmaceutical manufacturer is concerned that the impurity concentration in pills does not exceed 4%. It is known that from a particular production run, impurity concentrations follow a normal distribution with standard deviation 0.8%. A random sample of 100 pills from a production line was checked, and the sample mean impurity concentration was 4.12%. (a) Test the null hypothesis that the population mean impurity concentration is 4% against the alternative that it is greater than 4%. The significance level of this test is 5% (b) Find the power of a 5%-level test rejecting the null hypothesis when the true mean impurity concentration is 4.3%.

First, think of what you know. you know that the number t the end of the equation will need to be subtracted because it is the money he lost from buying the lawn mower. and your first two weeks have negative profit, so that tells you that c and d are wrong. now you can plug any of the weeks into a and b to see which one works. i'll start with plugging week 1 into a.this isn't right because it says your answer for week one should be -90.so now we need to try the same thing with b.this one got you the right answer, (sometimes if you only check with one of the weeks multiple will work so you need to check with more of the weeks, but it worked out fine here)this means that b is the correct answer.let me know if you need more clarification. i hope this : )