Advanced level maths. hypothesis testing. need helps.

An accountant wishes to investigate the figures provided by credit card companies for the amount of loans borrowed by each client, $x. He carries out an online survey from clients in a certain company. The responses from a random sample of 40 clients are summarised by x=38100,(xx)2=731800. (i) Calculate unbiased estimates of the population mean and variance of the amount of loans borrowed by each client, correct to 2 decimal place. The company claims that its clients will borrow $1000 on average (ii) Test, at the 5\% level of significance, whether the mean amount of loans borrowed by the clients differs from $1000. (iii) Explain, in the context of the question, the meaning of 'at the 5% level of significance'. The company revised their loan policy and the new population standard deviation is known to be 250 . A new random sample of 40 clients is taken and the mean amount of loans borrowed for this sample is $k. A test at the 5\% significance level indicates that the null hypothesis would not be rejected for this revised loan policy. (iv) Find the range of values of k