Albert,

Question1

Your aim is to get the most utility for every $1 you spend.

At each step, work out the marginal utility you getper $1spent on each product. Consumer will choose the one that has the highest figure (provided he has enough money left to afford it)

So, to start with you have:

(A) 18/2 =9

(B) 39/3 = 13

(C) 12/1 = 12

So the highest utility per $ comes from B, and he buys one of those.

Now he has $24 and has to decide what to buy next:

(A) 18/2 =9

(B) 36/3 = 12

(C) 12/1 = 12

He is tied between B and C. You can choose which one he will buy (ill pick B again)

Now he has $22 and has to decide what to buy next

(A) 18/2 =9

(B) 33/3 = 11

(C) 12/1 = 12

The best value is (C), so he buys one of them

Now he has $21 and has to decide what to buy next.....

You dont need to do this full reasoning every time (although you can if you want). It will be quicker for you to produce a full table of (Marginal Utility / Price).

Question 2

You have already worked out the total cost, so you just need the total revenue.

This is: (sale price) * (total product output).

You didn't give the sale price but from your screenshot it looks like it might be $32.

Profits are:

(total revenue) - (total cost)

Once you have worked out the profit at every output level, just see which output level has the highest profit.