I Question 3 (5 marks} According to the previous census, the mean income of all working mothers was $600 with a standard deviation of $120. A politician claims that the mean income of all working mothers has increased. To test the politician's belief, a survey was conducted among 400 working mothers. Let Y denote the mean of a random sample of size n = 400. Our decision is to reject Ho when i 2' $609.87