Answer: 15.08
Explanation:
The test statistic for difference between two population means is given by :-

Given : State A State B
Sample size 80 50
Mean interest rate (%) 4.0 4.5
Population variance 0.04 0.03
Then , the test statistic for difference between two population means will be :-

Hence, the value of the test statistic will be 15.08 .