Suppose a multi-class logistic regression has been used as a model for digit recognition. What is the probability expression P(Y=k|x=x) equal to, for k=1 to K-1?
a) (exp(w_k^(T)x))/(1+Σ_(l=1)^(K-1) exp(w_l^(T)x))
b) (exp(w_k^(T)x))/(1+Σ_(l=1)^(K) exp(w_l^(T)x))
c) (exp(w_k^(T)x))/(1+Σ_(l=1)^(K+1) exp(w_l^(T)x))
d) (exp(w_k^(T)x))/(1+Σ_(l=1)^(K-2) exp(w_l^(T)x))