Concept:
The rate per metre of fencing is calculated by
\[
\text{Rate per metre}=\frac{\text{Total cost}}{\text{Total length of fencing}}
\]
For a rectangular field, total length of fencing is its perimeter:
\[
\text{Perimeter}=2(l+b)
\]
Step 1: Check Statement I.
Statement I gives only the area:
\[
lb=10000
\]
But from area alone, we cannot find the perimeter.
For example, many rectangles can have area \(10000\) but different perimeters.
So Statement I alone is not sufficient.
Step 2: Check Statement II.
Statement II gives only total cost:
\[
\text{Total cost}=100000
\]
But the fencing length is unknown.
So Statement II alone is not sufficient.
Step 3: Combine both statements.
Even using both statements, we know:
\[
lb=10000
\]
and
\[
\text{Total cost}=100000
\]
But we still do not know \(l+b\), so we cannot determine the perimeter.
Therefore, the rate per metre cannot be determined.
Step 4: Final answer.
\[
\boxed{\text{Both statements together are not sufficient}}
\]