PROBLEM $3$

Consider the gear train shown in the illustration.

A gear with $12$ teeth is fixed on shaft $A.$

Gears with $50$ teeth and $20$ teeth are fixed on shaft $B.$

Gears with $72$ teeth and $25$ teeth are fixed on shaft $C.$

A gear with $80$ teeth is mounted on shaft $D.$

Suppose that shaft A is running at a speed of $1800$ rpm $.$ State all speeds in units of rpm $.$

a$)$ What is the speed of shaft $B?$

b$)$ What is the speed of shaft $C?$

c$)$ What is the speed of shaft $D?$