$A$ dietician has to develop a special diet using two foods $P$ and $Q$. Each packet (containing $30 \, g$) of food $P$ contains $12$ units of calcium,$4$ units of iron,$6$ units of cholesterol,and $6$ units of vitamin $A$. Each packet of the same quantity of food $Q$ contains $3$ units of calcium,$20$ units of iron,$4$ units of cholesterol,and $3$ units of vitamin $A$. The diet requires at least $240$ units of calcium,at least $460$ units of iron,and at most $300$ units of cholesterol. How many packets of each food should be used to maximize the amount of vitamin $A$ in the diet? What is the maximum amount of vitamin $A$ in the diet?
- A
$40$ packets of $P$ and $15$ packets of $Q$; Maximum vitamin $A = 285$ units
- B
$15$ packets of $P$ and $40$ packets of $Q$; Maximum vitamin $A = 210$ units
- C
$20$ packets of $P$ and $40$ packets of $Q$; Maximum vitamin $A = 240$ units
- D
$10$ packets of $P$ and $50$ packets of $Q$; Maximum vitamin $A = 210$ units