options crt;  ? 3e3
in weird;
smpl 1,15;
print y x1 x2;
corr y x1 x2;  ? (a)
olsq y c x1;
 rename @rsq rsq1;
olsq y c x2;
 rename @rsq rsq2;
set sumrsq = rsq1+rsq2;  ? (c)
olsq y c x1 x2;
print @rsq sumrsq;  ? (d)