A discrete random variable gives the number of passengers boarding a bus during a 12-minute interval, with probability distribution shown below:
| 0 | 1 | 2 | 3 | 4 | |
|---|---|---|---|---|---|
| 0.1 | 0.3 | 0.2 |
A voucher value (in dollars) is determined by the formula (so the voucher increases by for each extra passenger).