You receive a gift certificate for a clothing store and plan to use it to buy T-shirts and sweatshirts. Choose a situation in which you can buy 9 T-shirts and 1 sweatshirt, but you cannot buy 3 T-shirts and 9 sweatshirts. T-shirts cost $5, sweatshirts cost $10, the gift certificate is worth $120, and you want to buy at least 6 shirts total.

T-shirts cost $5, sweatshirts cost $20, the gift certificate is worth $80, and you want to buy at least 6 shirts total.

T-shirts cost $5, sweatshirts cost $10, the gift certificate is worth $120, and you want to buy no more than 10 shirts total.

T-shirts cost $5, sweatshirts cost $20, the gift certificate is worth $80, and you want to buy no more than 12 shirts total.

Write a system of inequalities that represents the situation chosen above. Let x be the number of T-shirts and y be the number of sweatshirts.