The following table gives the tariff [in paise per kilo-watthour (kWh)] levied by the UPSEB in 1994–95, in four sectors and the regions within them. The table also gives the percentage change in the tariff as compared to 1991–92.
| Sector | Region 1 | Region 2 | Region 3 | Region 4 | Region 5 | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| P/kWh | % incr. | P/kWh | % incr. | P/kWh | % incr. | P/kWh | % incr. | P/kWh | % incr. | |
| Sector 1 | $425$ | $+15$ | $472$ | $+5$ | $420$ | $-4$ | $415$ | $+8$ | $440$ | $+10$ |
| Sector 2 | $430$ | $+12$ | $468$ | $+8$ | $448$ | $+7$ | $423$ | $-3$ | $427$ | $+11$ |
| Sector 3 | $428$ | $+8$ | $478$ | $-4$ | $432$ | $+6$ | $441$ | $+10$ | $439$ | $+8$ |
| Sector 4 | $434$ | $-5$ | $470$ | $+15$ | $456$ | $+10$ | $451$ | $+12$ | $446$ | $-12$ |




| A | B | C | D | Average |
|---|---|---|---|---|
| 3 | 4 | 4 | ? | 4 |
| 3 | ? | 5 | ? | 4 |
| ? | 3 | 3 | ? | 4 |
| ? | ? | ? | ? | 4.25 |
| 4 | 4 | 4 | 4.25 |
For any natural number $k$, let $a_k = 3^k$. The smallest natural number $m$ for which \[ (a_1)^1 \times (a_2)^2 \times \dots \times (a_{20})^{20} \;<\; a_{21} \times a_{22} \times \dots \times a_{20+m} \] is: