GATE Civil Engineering (CE) 2017 Shift 2 Solved Paper

The infiltration capacity of a soil follows the Horton’s exponential model f = c₁ + c₂ e^–kt. 
During an experiment, the initial infiltration capacity was observed to be 200 mm/hr. After a long time the infiltration capacity was reduced to 25 mm/h, if the infiltration capacity after 1 hour was 90 mm/h the value of the decay rate constant k (in h^–1 up to two decimal places) is______