Imagine you are the sales manager for a large team of sales representatives. You are considering implementing a new compensation system and want to see if implementing the system will increase individuals' monthly sales. You examine the sales of 12 sales representatives who receive the new system, and 18 of which do not (use the old system). The sales representatives who received the new system had a mean monthly individual sales of $29,764, with a sample standard deviation of 4,041. The sales representatives who received the old system had mean monthly individual sales of $27,918, with a sample standard deviation of 4,971. Using this information, you want to perform a pooled t-test to determine if the new compensation system increases individuals monthly sales, with an alpha level of 0.05. What is the degree of freedom for the test statistic used in your analysis? Round your answer down to the nearest whole number.