A gambler has developed two strategies for betting in the game of blackjack.To test these strategies, he decides to go gambling at Honest Bob's Casino.He plays five sessions of blackjack using each of the two strategies (that is, the sample size for strategy 1 is 5 and the sample size for strategy 2 is also 5).He then records his profit from the two strategies for each of the five sessions (a negative profit indicates a loss).The goal of the gambler is to determine which of the two betting strategies will result in a higher mean profit.The 95% confidence interval for the true mean profit for strategy 1 minus the true mean profit for strategy 2 is (-110, 34).Assume random samples were taken from populations that were normally distributed.Assume equal population variances.

Pick the formula used to calculate the confidence interval above.