Throughput accounting

Yam Co (6/09 amended) is involved in the processing of sheet metal into products A, B and C using three processes, pressing, stretching and rolling. Like many businesses Yam faces tough price competition in what is a mature world market. The factory has 50 production lines each of which contain the three processes: Raw material for the sheet metal is first pressed then stretched and finally rolled. The processing capacity varies for each process and the factory manager has provided the following data: Processing time per metre in hours Pressing A) 0.50 B) 0.50 C) 0.40 Stretching a) 0.25 b) 0.40 c) 0.25 Rolling a) 0.40 b) 0.25 c) 0.25 The factory operates for 18 hours each day for five days per week. It is closed for only two weeks of the year for holidays when maintenance is carried out. On average one hour of labour is needed for each of the 225,000 hours of factory time. Labour is paid $10 per hour. The raw materials cost per metre is $3.00 for product A, $2.50 for product B and $1.80 for product C. Other factory costs (excluding labour and raw materials) are $18,000,000 per year. Selling prices per metre are $70 for product A, $60 for product B and $27 for product C. Yam carries very little inventory. Required: Calculate the throughput accounting ratio (TPAR) for each product assuming that the bottleneck process is fully utilised. * my question is that it says assuming that the bottleneck process is fully utilised and as i checked the answer of the question the PROCESSING time per metre in hours have been taken PRESSING ( usage of bottleneck resource in hours) but why not STRETCHING or ROLLING?