A geotechnical engineer is designing a foundation for a building on a clay soil with an undrained shear strength of 100 kPa. The foundation is rectangular, with dimensions of 5 m by 10 m. The building will have a weight of 500 kN, and the water table is located at a depth of 3 m below the foundation. The engineer wants to design the foundation to have a factor of safety of 3 against bearing capacity failure. Determine the safe bearing capacity of the soil, and calculate the required depth of the foundation.