The time required for 50 % consolidation of a 25 mm thick clay layer (drained at both top and bottom) in the laboratory is 2 min. 20 sec. How long (in days) will it take for a 3 m thick clay layer of the same clay in the field under the same pressure increment to reach 50 % consolidation? In the field, there is an impermeable rock layer at the bottom of the clay