Answer
The value of the function is\[f\left( 3.5 \right)=1.15\text{ dollars}\].
Work Step by Step
The cost of mailing a letter of weight 3.5 ounces is the value of the function at a weight of 3.5 ounces.
It can be observed from the given graph that the cost of $f\left( x \right)$ remains the same for the interval from 3 to 4 ($\$1.15$).
