On two soil samples, having a diameter of 3.8 cm, triaxial tests are performed, at cell pressures of 10 kPa and 20 kPa, respectively. In the first test failure occurs for an axial force of 22.7 N, and in the second test for an axial force of 44.9 N. Determine c and φ of this soil, assuming that there are no pore pressures.