area of the shaded part above or under the baseline

hello

i want a way so i can know the area of the shaded part above the base line and under it so i can multiple with the width of the road to get cut and fill informations

this my code till now

clc
clear
station = input('enter number of stations');
width = input('enter the width ');
compact = input('enter the compaction factor ');
x = 0:50:station*50;
y=1:station+1;
for i=1:station+1;
 y(i) = input('Please input the elevation ');
end
Mean=mean(y);
[Offset, fv] = fzero(@(b) trapz(x, y-b), 0);
y_above = y - Offset;
y_below = max(-y_above,0); % Take the part below y_split
y_above = max(y_above,0); % Take the part above y_split 
A_above = trapz(y_above);
A_below = trapz(y_below);
area(x,y,Offset);
grid on; set(gca,'layer','top');