Suppose that X1, X2, . . . , Xm, representing yields per acre for corn variety A, constitute a random sample from a normal distribution with mean μ1 and variance σ2. Also, Y1 Y2, . . . , Yn , representing yields for corn variety B, constitute a random sample from a normal distribution with mean μ2 and variance σ2. If the X's and Y 's are independent, find the MLE for the common variance σ2. Assume that μ1 and μ2 are unknown.