Throughput accounting question (BPP revision kit question #38)

For the following question, I do not understand why conversion cost is not put into consideration.

Question #38 :

A manufacturing company uses machine C, which is operational for five hours a day to manufacture four products: W, X, Y and Z. Factory costs are $150,000 per day. The company uses throughput accounting and its objective is to maximize profits.

Information relating to these products is as follows:

Products——-Production rate per machine hour (units)
—–W——————————–200
—–X———————————500
—–Y———————————400
—–Z———————————350

Selling Price per unit—-Material cost per unit—–Conversion cost per unit
———-$350————————–$120—————————-$40
———-$190————————–$95——————————$25
———-$270————————–$160—————————-$20
———-$215————————–$75——————————$35

If the company is not able to increase the availability of machine C’s
operational hours, what is the production ranking of product Y?

Options:
A. First
B. Second
C. Third
D. Forth

The correct answer is D (fourth)

——————————————————————————-

In the book it says that TPAR is not needed as they are all produced from same factory.
I thought I should add the conversion cost to the factory cost of $150,000
because each product would have different coversion cost per per hour.

Is the conversion cost included in the factory cost of $150,000 ?

Thank you !