This might have made sense to you if this was plus right over here, but it doesn't matter if we are adding or subtracting, and these are truly independent variables, then regardless of whether we're adding or subtracting, you would add the variances. And so we can figure this out. This is going to be equal to, the standard deviation of variable M is eight. So eight squared is going to be 64. And then we have six squared. This right over here is six. Six squared is going to be 36.