In an $\text{ac}$ main, the $\text{rms}$ voltage $V_{ac}$, $\text{rms}$ current $I_{ac}$ and power $W_{ac}$ are measured as: $V_{ac}=100 \: V \pm 1\%, I_{ac} = 1 \: A \pm 1\%$ and $W_{ac}=50 \: W \pm 2\%$(errors are with respect to readings). The percentage error in calculating the power factor using these readings is
- $1\%$
- $2\%$
- $3\%$
- $4\%$