# Math Help - Open and metric

1. ## Open and metric

can someone help me to solve these problems in details??
Consider A =(0,1)× R. Is A open w.r.t. the topology induced by the French railway metric in R2? how
Is the the French railway metric defined as follows: $d((x_1,y_1),(x_2,y_2))=|x_1-x_2|+|y_1-y_2|$? Do you know how open balls under this metric look like?