A manufacturer buys 75% of its steel from Supplier A with an average tensile strength of 460 MPa and a standard deviation of 20 MPa. The rest of the steel is bought from Supplier B with an average tensile strength of 500 MPa and a standard deviation 25 MPa. If a piece of steel is found to have a strength of over 470 MPa, what is the probability it was produced by Supplier B? (Assume steel strength is normally distributed.) A. 0.61 B. 0.05 C. 0.49 D. 0.25