Let C represent a function in the following way:
C(x) where, x is the grams of bolts.
Then, a function rule that represent the situation will be:
C(x) = 3.29x
For example
If we have 1 gr of bolts then the cost is:
C(1) = 3.29(1) = 3.29
On the other hand, if we have 0 gr of bolts, then the cost is:
C(0) = 3.29(0) = 0
So our equation match. We can conclude that a function that represent the situation will be:
C(x) = 3.29x