For each subset of R, give its supremum and its maximum, if they exist. Otherwise, write "none." (a) {1,3} (c) [0,4] (e) {2:nEN} 2) {":"EN} (b) {n, 3} (d) (0,4) (f) {1-1:n=N} () {(-1*(1+1};nN} a) :neN