$29)$ The Work in Process $-$ Assembly account would be credited and the Work in Process $-$ Packaging account would be debited when:

a$.$Goods are transferred from Assembly to Packaging.

b$.$Goods are transferred from Packaging to Assembly.

c$.$The units are complete and ready for sale.

d$.$The number of units started during the period is greater than the number of units in process at the end of the period.