A kindergarten teacher bought $21 worth of stickers and cardstock for his class. The stickers cost $1.50 a sheet and the cardstock cost $3.50 per pack. The equation 1.5s+3.5c=21 represents the relationship between sheets of stickers, s, packs of cardstock, c, and the dollar amount a kindergarten teacher spent on these supplies.

a. Explain how we can tell that this graph represents the given equation.

b. What do the vertical and horizontal intercepts, (0,6) and (14, 0), mean in this situation?