The Following Information Relates to Lancashire Manufacturing: to Produce a Unit

The following information relates to Lancashire Manufacturing: To produce a unit of product: $\begin{array}{ll}\text { Mixing dep artment } & 3 \text { minutes per unit } \\\text { Colding department } & 5 \text { minutes per unit } \\\text { Casting department } & 7 \text { minutes per unit } \\\text { Finishing department } & 4 \text { minutes per unit }\end{array}$ There is a wait time of 8 minutes before the mixing department begins a batch, 5 minutes between the mixing and molding departments, a move and pre-wait between molding and casting of 10 minutes, and a move and pre-wait between the casting and finishing departments of 12 minutes.
What is the production rate?

A) 8.6 units per hour
B) 7 units per hour
C) 21 units per hour
D) 19 units per hour