Here is the questions I'm working on. I can't figure out the answer to b.) I'm not sure how they arrived at the number of units in the example on Chegg

I got the answer to a.) X-10 = $ 400 / X-20 = $ 750 / X-40 = $ 1,175

Washington, Inc., makes three models of motorized carts for vacation resorts, X-10, X-20, and X-40. Washington manufactures the carts in two assembly departments: Department A and Department B. All three models are processed initially in Department A, where all material is assembled. The X-10 model is then transferred to finished goods. After processing in Department A, the X-20 and X-40 models are transferred to Department B for final assembly, and then transferred to finished goods.

There were no beginning work-in-process inventories on April 1. Data for April are shown in the following table. Ending work in process is 30 percent complete in Department A and 60 percent complete in Department B. Conversion costs are allocated based on the number of equivalent units processed in each department.

	Total			X-10			X-20			X-40
Units started					490			370			260
Units completed in Department A					360			250			170
Units completed in Department B								230			160
Materials	$	352,000		$	36,750		$	120,250		$	195,000
Conversion costs:
Department A	$	286,650
Department B		40,800
Total conversion costs	$	327,450

Required:

(a)	What is the unit cost of each model transferred to finished goods in April? (Do not round intermediate calculations. Round final answers to the nearest dollar amounts and units.)

(b)	What is the balance of work-in-process inventory on April 30 for Department A? Department B? (Do not round intermediate calculations. Round final answers to the nearest dollar amounts and units.)