求解matlab编程时遇到语法问题的解决办法

[籽籽籽晴]

ua=0:1:71;
N=length(ua);n=0;T=0;Ft=0;ad=0*ua;area=0*ua;
for i=1:N
k=i;
if ua(i)<=20
T=1146+0*ua(i);
else
T=443.527-0.165465*(n2-4518.25)+0.0000360772*(n2-4518.25).^2-0.00000000361349*(n2-4518.25).^3;
end
n=ua(i)*(im*i0/r)/0.377;
Ft=T*im*i0*Nt/r;
f=0.0076+0.000056*ua(i);
Fw=Cd*A*ua(i).^2/21.15;
D=(Ft-Fw)/G;
ad(i)=1.29/9.8*(D-f);
area(i)=0.01.*ad(i)/3.6;
AREA=area(1:k);
t(i)=sum(AREA);
end
In an assignment A(I) = B, the number of elements in B and I must be the same.