Mary works selling cards over the telephone. She sells two types of cards: birthday cards and holiday cards. Mary makes $2 for each pack of birthday cards she sells and $2.50 for each pack of holiday cards she sells. She
can work no more than 10 hours per week and it takes her an average of 15 minutes to sell one pack of birthday
and an average of 20 minutes to sell one pack of holiday cards. If she can sell no more than 35 packs of cards,
how many packs of each type of card should she sell to make the most money?