A procurement specialist has purchased 25 resistors from vendor 1 and 30 resistors from vendor 2. Let X1,1, X1,2, , X1,25 represent the vendor 1 observed resistances, which are assumed to be normally and independently distributed with mean 100 ohms and standard deviation 1.5 ohms. Similarly, let X2,1, X2,2, , X2,30 represent the vendor 2 observed resistances, which are assumed to be normally and independently distributed with mean 105 ohms and standard deviation of 2.0 ohms. What is the sampling distribution of X1 – X2?