Which of the following domains are closed and which are bounded?
(a) {(x,y)∈R2:x2+y2≤1}
(b) {(x,y)∈R2:x2+y2<1}
(c) {(x,y)∈R2:x≥0}
(d) {(x,y)∈R2:x>0,y>0}
(e) {(x,y)∈R2:1≤x≤4,5≤y≤10}
(f) {(x,y)∈R2:x>0,x2+y2≤10}