$3.$ To classify a soil sample according to USCS soil classification system, grain size distribution and Atterberg limit tests were conducted in the laboratory. The cumulative grain size frequency curve is given in the attachment. The Plastic limit of the soil is $36\mathrm{.}7\%$ and the plasticity index is $19\mathrm{.}2\%.$

a$.$Determine the percentage of gravel, sand, silt and clay.

b$.$Determine the liquid limit of the soil.

c$.$Classify the soil according to USCS classification system.

d$.$Based on grain size and Atterberg limit parameters comment on the physical characteristics of the soil.