LIMITING FACTOR ANALYSIS

hi,
there is a difficulty related to the calculation of of limiting factor per unit in question given below
Data:
A company x makes three products A B C …..the cost structure for a batch of five of each is as follows
labor (at 250$ per hr) = 50$ 125 $ 62.5$ respectively A B C {this is limiting factor so providing only relevant data }
currently each day the company makes and sell max demand of A 400 units B 300 units C 600units.
REQUIREMENT> now the question ask the optimum production plan and profit that this gives if labor hrs available to 60 per day …….I have problem with the calculation of labor hours/loaf ….book answer is 4 10 5 respectively A B C how we calculate it ????