Problem 3. [ 20 ponits] An engineer performed a series of tests to measure a concentration of boron in a coolant of the chemical shim system of a nuclear reactor. The mean value of the boron concentration was evaluated as 225ppm. The following systematic and random source errors were found in three sets of measurements: (bC)1=12ppm,(sC)1=11ppm,v1=25;(bC)2=14ppm,(sC)2=15ppm,v2= 19;(bC)3=13ppm,(sC)3=12ppm,v3=28. Determine the uncertainty in the mean value at 95% confidence