Kelly sells magazine subscriptions after work. the half-year subscriptions cost $12, and the full-year subscriptions cost $20. today, kelly has 20 subscription cards with her, only one subscription can be ordered on each card, and she wants to sell subscriptions totaling at least $300. if the solution region represents the amount of half-year and full-year magazine subscriptions kelly needs to sell to reach her goal, which graph's shaded area represents the solution region?