Answer to question 1

The given line integral is

We evaluate the first line integral from

to

.

An equation of the straight line joining

and

in the xy plane is

.

The first line integral now becomes,

We evaluate the second line integral from

to

.

An equation of the straight line joining

and

in the xy plane is

.

The second line integral now becomes,

We now evaluate the third line integral from

to

.

An equation of the straight line joining

and

in the xy plane is

.

The third line integral now becomes,

We now evaluate the fourth line integral from

to

.

An equation of the straight line joining

and

in the xy plane is

.

The fourth line integral now becomes,

We now add all the line integrals to get,

Answer to question 2

According to the Green's Theorem,

.

This implies that,

This simplifies to

We evaluate the inner integral to get,

We now integrate again, to obtain,