A lab scientist is interested in whether lab rats that grow up alone grow as large as lab rats that grow up with other rats around them to play with. He randomly selects 10 young rats with approximately the same age and size. Five of these will spend the next four monthsalone and the other five rats will each have three other rats to play with during the same time. After four months, the scientist measures the abdomen circumference of all the rats (in mm). The results are shown below: Alone group (#1) 110 123 113 103 120 Play group (#2) 119 125 131 128 136 The sample means and sample standard deviations are = 113.8 and s1 = 7.98, = 127.8 and s2 = 6.38 The sample standard deviations are fairly close in value. Based on these estimates, it is reasonable to assume that the two population variances are equal. What is the value of the estimate of the common variance?