Pandi 夫人想通过航空邮件寄信到国外。
寄往两个国家的航空邮费如下表所示。

航空邮费	泰国	澳大利亚
首 25 g	$0.90	$1.50
每增加 10 g 或以下	$0.20	$0.30

Pandi 夫人想寄一封重 33 g 的信到泰国，以及一封重 42 g 的信到澳大利亚。她一共需要支付多少钱？ 答案：$ ___

1. Calculate the postage for the letter to Thailand

Mass of letter to Thailand = $33$ g.
First $25$ g costs $\char36{}0.90$.
Remaining mass = $33 - 25 = 8$ g.
Since $8$ g is less than $10$ g, it counts as $1$ additional block.
Cost for additional mass = $1 \times \char36{}0.20 = \char36{}0.20$.
Total cost for Thailand = $\char36{}0.90 + \char36{}0.20 = \char36{}1.10$.

2. Calculate the postage for the letter to Australia

Mass of letter to Australia = $42$ g.
First $25$ g costs $\char36{}1.50$.
Remaining mass = $42 - 25 = 17$ g.
Since $17$ g is between $10$ g and $20$ g, it counts as $2$ additional blocks of $10$ g.
Cost for additional mass = $2 \times \char36{}0.30 = \char36{}0.60$.
Total cost for Australia = $\char36{}1.50 + \char36{}0.60 = \char36{}2.10$.

3. Calculate the total amount Mrs Pandi needs to pay

Total cost = $\char36{}1.10 + \char36{}2.10 = \char36{}3.20$.