Compare two independent sample means

Two firms A and B manufacture components with mean breaking strengths 6 kN and 5.5 kN and standard deviations 0.4 kN and 0.2 kN respectively. Random samples of 100 components from A and 50 from B are tested. Find the probability that the mean strength from A is between 0.45 kN and 0.55 kN more than that from B.