Given the following calling sequences and ass

ing is used, what variables are visible during execution of the last func$-$

tion called? Include with each visible variable the name of the function in

which it was defined.

a$.$ main calls fun$1$; fun$1$ calls fun$2$; fun$2$ calls fun$3.$

b$.$ main calls fun$1$; fun$1$ calls fun$3.$

c$.$ main calls fun$2$; fun$2$ calls fun$3$; fun$3$ calls fun$1.$

d$.$ main calls fun$3$; fun$3$ calls fun$1.$

e$.$ main calls fun$1$; fun$1$ calls fun$3$; fun$3$ calls fun$2.$

f$.$ main calls fun$3$; fun$3$ calls fun$2$; fun$2$ calls fun$1.$