Answer:
$1.84
Explanation:
In a certain country, a letter upto 1 ounce requires postage of = $0.42
and each additional ounce (or fraction of an ounce) has an additional cost.
The function which represents this situation :
![f(c)=[0.42+0.20(x-1)]](https://img.qammunity.org/2019/formulas/mathematics/middle-school/9j1ia8kg1zjpou69wiquvl69waz0qatve5.png)
The weight of Josiah's first letter = 2.9 ounces (x= 2.9)
![f(1)=[0.42+0.20(2.9-1)]](https://img.qammunity.org/2019/formulas/mathematics/middle-school/tkef6wi7tdmtkg7ten96wz9hhe5llj5lx9.png)


f(1) = 0.80
![f(2)=[0.42+0.20(4.1-1)]](https://img.qammunity.org/2019/formulas/mathematics/middle-school/v801ld74clno3vvj1tizrsld6ysl51b6sy.png)


f(2) = 1.04
0.80 + 1.04 = $1.84
The total amount is $1.84, Josiah can expect to pay for postage