Alex bought all the string needed for $125.
It costs $18 for the remaining materials to make each puppet.
So if we closely observe then we see that here $125 is the fixed cost because its not going to change with number of puppets.
And the variable cost is $18.
In this case we can model a Total cost function C(x) for for x number of puppets as below
[tex] C(x)=125+18x\\
\\
\text{Here x is the number of puppets}\\
\\
\text{Since in our case the number of puppets is 50 so replace x by 50 we get }\\
\\
C(50)=125+18*50\\
\\
C(50)=125+900\\
\\
C(50)=1025 \ dollar. [/tex]
The total cost to make 50 puppets=$1025
