Please help me solve this problem step by step. I need to prepare for the Exam. Thank You.

Salary information regarding male and female employees of a large company is shown below.

Male Female

Sample Size 64 36

Sample Mean salary (in $1000) 44 41

Population Variance 128 72

The point estimate of the difference between the means of the two populations is

a. -28

b. 3

c. 4

d. -4