A specimen of sand at the field density is known to have a (1/ 3) max of

A specimen of sand at the field density is known to have a (σ1/ σ3) max of 3.8. If such a specimen is hydrostatically consolidated to 1180 kPa in a triaxial test apparatus, at what effective confining pressure will the specimen fail if the vertical stress is held constant? (This is a lateral extension test.)?