Samples of damp sand are tested in direct shear (samples are tested at the in situ water content). The procedure involves two scparate tests, with different normal loads for each test. In test one. using a normal loading which cavses a compressive stress equal to $50 \mathrm{kPa}$, the sample is failed at a shear stress equal to $33 \mathrm{kPa}$. For test two, the normal stress is $80 \mathrm{KPa}$ and the sample sheass at a stress of $51 \mathrm{kPa}$. Use this test data to determine the angle of internal friction and the value of apparent cohesion for this sand.