$(20$ points$)$ Due to some reason $($excavation or scouring$),$ soil depth decreased from $H$ to $h$ as shown in the figure below.

$=$ soil unit weight. Please assume there is no water table.

$(1)$ Please calculate the effective stress at point $A($before excavation$)$ and point $B($after excavation$).$

$(2)$ Please estimate the over$-$consolidated ratio $($OCR$)$ after the excavation.

$(3)$ Then, determine if soil B is over$-$consolidated or normally consolidated.