Concept:
Simple interest for one year is calculated by the formula
\[
SI=\frac{P\times R\times T}{100}
\]
where
\[
P=\text{Principal amount}
\]
\[
R=\text{Rate of interest}
\]
\[
T=\text{Time in years}
\]
Since the question asks for yearly simple interest,
\[
T=1
\]
Step 1: Check Statement I.
Statement I says:
\[
P=10000
\]
But the rate of interest is not given.
So simple interest cannot be found using Statement I alone.
Therefore, Statement I alone is not sufficient.
Step 2: Check Statement II.
Statement II says:
\[
R=8\%
\]
But the principal amount is not given.
So simple interest cannot be found using Statement II alone.
Therefore, Statement II alone is not sufficient.
Step 3: Combine both statements.
Using both statements,
\[
P=10000,\qquad R=8,\qquad T=1
\]
So,
\[
SI=\frac{10000\times 8\times 1}{100}
\]
\[
SI=800
\]
Thus, both statements together are sufficient.
Step 4: Final answer.
\[
\boxed{\text{Both statements together are sufficient, but neither alone is sufficient}}
\]