Answer
a) See the explanation below.
b) See the explanation below.
Work Step by Step
a) Suppose a function is considered to be written as $f(x,y)$ with two variables $x,y$ in a set of domain D of real numbers which is continuous at the point $(a,b)$ along any closed path which lies inside the domain when it follows the below condition
$\lim\limits_{(x,y) \to (a,b)}f(x,y)=f(a,b)$
b) This means that the graph for the function $f(x,y)$ will be a surface or solid undisturbed surface without any holes or breaks.
