Answer:
54 cents
Step-by-step explanation:
The cost of bookmarks relating to the number of bookmarks is given by the graph shown. Therefore:
From the graph, we can determine the relationship between the cost of bookmarks and the number of bookmarks by using two points. The equation of a line passing through points
is:

From the graph, y represents the cost of bookmarks in cents and x represent the number of bookmarks. we can see that it passes through the point (2, 30) and (7, 90). Hence:

The cost of 4 bookmarks (x = 4):
y = 12(4) + 6
y = 54 cents