Answer:
And we can assume a normal distribution and then we can solve the problem with the z score formula given by:
And replacing we got:
We can find the probability of interest using the normal standard table and with the following difference:
Step-by-step explanation:
Let X the random variable who represent the expense and we assume the following parameters:
And for this case we want to find the percent of his expense between 38.6 and 57.8 so we want this probability:
And we can assume a normal distribution and then we can solve the problem with the z score formula given by:
And replacing we got:
We can find the probability of interest using the normal standard table and with the following difference: