A researcher collects two independent random samples of sizes n1=31n1=31 and n2=36n2=36 , and computes the means, x⎯⎯⎯1x¯1 and x⎯⎯⎯2,x¯2, and the standard deviations, s1s1 and s2,s2, of each sample. She plans to use a tt ‑test to determine if there is a difference between the two population means, µ1μ1 and µ2.μ2. She does not know the population standard deviations, nor does she have any reason to believe that they are equal. Using the most conservative approach, calculate how many degrees of freedom, df, are associated with this hypothesis test. Express your answer as an integer.