customers go through steps B$1$ and B$2$ and then can be served at either of the two barbers at step B$3.$ The process ends for all customers at step B$4.$ The numbers in parentheses indicate the minutes it takes that activity to process a customer.

B$1$

B$2$

B$4$

B$3-$a

B$3-$b

$(7)$

$(8)$

$(10)$

$(15)$

$(12)$

In the diagram, there are $5$ circles labeled inside each circle using labels B$1,$ B$2,$ B$3-$a$,$ B$3-$b$,$ and B$4.$ There is a number inside parentheses below each label. Also, there are arrows that show the flow through the circles from B$1$ to B$4$ as follows: Circle B$1(7)$ connects to circle B$2(8),$ circle B$2(8)$ connects to circle B$3-$a $(10)$ and to circle B$3-$b $(15),$ and circles B$3-$a $(10)$ and B$3-$b $(15)$ connect to circle B$4(12).$

Part $2$

a$.$ How long does it take the average customer to complete this$$ process?

$$

enter your response here minutes. $($Enter your response rounded to one decimal$$ place.$)$

Part $3$

b$.$ What single activity is the bottleneck for the entire$$ process?$$B

$$

enter your response here

Part $4$

c$.$ How many customers can this process serve in an$$ hour?

$$

enter your response here customers per hour. $($Enter your response as an$$ integer.$)$