A health-drink company’s R&D department is trying to make various diet formulations, which can be used for certain specific purposes. It is considering a choice of 5 alternative ingredients \( (O, P, Q, R, S) \), which can be used in different proportions in the formulations.
The cost per unit of each ingredient is: \[ O: \text{Rs. } 150,\quad P: \text{Rs. } 50,\quad Q: \text{Rs. } 200,\quad R: \text{Rs. } 500,\quad S: \text{Rs. } 100 \]
The table below gives the composition of these ingredients:
| Ingredient | Carbohydrate % | Protein % | Fat % | Minerals % |
|---|---|---|---|---|
| O | 50 | 30 | 10 | 10 |
| P | 80 | 20 | 0 | 0 |
| Q | 10 | 30 | 50 | 10 |
| R | 5 | 50 | 40 | 5 |
| S | 45 | 10 | 0 | 5 |




| 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: