Final answer:
The total amount credited to Materials Inventory for Lanyard in 2018 is $140,000, which equals the materials placed into production as given in the question.
Step-by-step explanation:
The question asks to determine the total amount credited to Materials Inventory for Lanyard in 2018. Since the information given includes the amount of materials placed into production, but not the initial or final materials inventory, we cannot calculate changes to the Materials Inventory account directly from the given data. However, assuming that the materials placed into production represent all materials used and hence were moved from Materials Inventory to Work-in-Process Inventory, then the total amount credited to Materials Inventory for Lanyard in 2018 would be the same as the materials placed into production, which is $140,000.