Units started and completed (Process Costing)

A company which operates a process costing system had work-in-progress at the start of last month of 300 units (valued at $1,710) which were 60% complete in respect of all costs. Last month a total of 2,000 units were completed and transferred to the finished goods warehouse. The cost per equivalent unit for costs arising last month was $10. The company uses the FIFO method of cost allocation. What was the total value of the 2,000 units transferred to the finished goods warehouse last month? A $19,910 B $20,000 C $20,510 D $21,710 Hello. I know the answer for the question is A and the units started and completed is 1700 however it's kind of confusing me since the same logic doesn't seem to be applying to the question below: The following Information relates to process 3 of a 3-stage production process for the month of January 20X4. Opening Inventory 300 units complete as to: Materials from Process 2 100% $4400 Added materials 90% $1150 Labour 80% $540 Production overhead 80% $810 In January 20X4, a further 1800 units were transferred from process 2 at a valuation of $27000. Added materials amounted to $6600 and direct labor to $3270. Production overhead is absorbed at the rate of 150% of direct labor cost. Closing inventory at 31, January 20X4 amounted to 450 units, complete as you: Process 2 materials 100 Added materials 60% Labour and overhead 50% DR Opening WIP 300units $6900 Input from P2 1800units $27000 Added materials 6600 Direct Labour 3270 Production Overhead 4905 CR Opening WIP to to completed 300units $7320 + Units started and completed 1350units $32400 = Output 1650units $39720 Closing WIP 450units $8955 Does someone has a clear formula for finding units started and completed? Usually I just do Input-Closing WIP but that doesn't seem to be working in the first example.