Answer: Option 'D' is correct.
Step-by-step explanation:
Let the number of wedding invitations be represented by x axis.
Let the cost of wedding invitations be represented by y-axis.
So, At cost of $210, a printer will produce 80 wedding invitations.
At cost of $290, a printer will produce 120 wedding invitations.
So, we have (80,210) and (120,290)
So, our equation of slope will become:

We need to find the cost of 60 (= x) invitations:

Hence, Option 'D' is correct.