Let {(1, 2); (0, 1); (-1, 0)} be a set of data points {(xi, yi), i = 1, 2, 3} ⊆ ℝ². Write the cost function for geometric PCA (use d = 1).

a) f(x)=x ^2+y ^2
b) f(x)=x
c) f(x)=xy
d) f(x)=x+y