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