Two soil specimens with identical geometric dimensions were subjected to failing head permeability tests in the laboratory under identical conditions. The fall of water head was measured after an identical time interval. The ratio of initial to final water heads for the test involving the first specimen was $1.25$. If the coefficient of permeability of the second specimen is $5$-times that of the first, the ratio of initial to final water heads in the test involving the second specimen is

- $3.05$
- $3.80$
- $4.00$
- $6.25$