In order to estimate the difference between the average hourly wages of employees of two branches of a department store, two independent random samples were selected and the following statistics were calculated.

	Downtown Store	North Mall Store
Sample size	36	30
Sample mean	$11	$9
Sample standard deviation	$4	$2

A 95% interval estimate for the difference between the two population means (Downtown Store - North Mall Store) is _____.

a. $1.24 to $2.76

b. $0.73 to $3.27

c. $0.48 to $3.52

d. $0.51 to $3.49