SAT Linear equations in one variable Question

A machine makes 9-inch, 8-inch, and 3-inch parts. During a certain day, the number of 9-inch parts that the machine makes is 4 times the number n of 8-inch parts, and the number of 3-inch parts is 15. During this day, the machine makes 100 parts total. Which equation represents this situation? A. $9(4n)+8n+3(15)=100$ B. $9n+8n+3n=100$ C. $4n+15=100$ $$5n+15=100$$