Amy has purchased a basic letterpress kit for $141. She plans to make wedding invitations. She estimates that the cost of the paper and envelope for each invitation is $3. Model this situation with a rational function that gives the average cost of a wedding invitation when the cost of the kit is included in the calculation. Use the graph of the function to determine the minimum number of invitations that brings the average cost below $5. The minimum number of wedding invitations that brings the average cost
below $5 is
.