Step 3) Correlate isolation (Fractional activity) and a Goal metric, G(t) :

    𝐶(𝑅𝐴,𝐺) = 1/𝑇 ∫〖𝑅𝐴(𝑡)∗𝐺(𝑡)𝑑𝑡〗

Note:
    C is positive when % A ini < % A opt
    C is negative when % A ini > % A opt and
    C = 0 when % A ini = % A opt

Therefore, C can be used to show if % Activity area A is too big, too small or “just right.” We have our feedback signal!