Question $2(20$ marks$)$:

The grain$-$size distribution of three inorganic soils $($labeled $A,B,$ and C $)$ and one organic soil $($labeled D$)$ are shown in Figure below.

a$)(10$ marks$)$ Which one of the three inorganic soils has the highest uniformity coefficient $C_u$ and which one has the lowest coefficient of gradation $C_c?$

b$)(10$ marks$)$ Classify soil D according to the USCS classification system; assume its liquid and plastic limits are $52\%$ and $22\%,$ respectively and determine the group symbol and group name.