Overhead cost

Hello sir
Hope this massage finds you well
Can you please assist me with this question MA1 chapter 7 (overhead costs)

A business has two production departments, , assembly and polishing. One of the products made in these departments is the Stun. Details for these departments and the Stun are as follows:

For assembly cost center

Overhead 94800
Labour hours 20000
Machine hours 60000
Stun labour hour per unit 3 hour
Stun machine hour per unit 4 hour

For polishing cost center

Overhead 74800
Labour hours 40000
Machine hours 15000
Stun labour hour per unit 5 hour
Stun machine hour per unit 2 hour

Overheads in the assembly department are to be absorbed on the basis of machine hours and in the polishing department on the basis of labour hours.
How much overhead in total would be included in the cost of a Stun?

A. $3.45
B. $8.48
C. $10.06
D. $15.67

Actually sir I correctly calculate the overhead obsorption rate for both polishing and assembly department

Which overhead obsorption rate for assembly department is 1.58$ per machine hour
And for polishing department it’s 1.87$ per labour hour

But when I calculate the overhead in total for stun I assume that stun take 4 machine hour in assembly department and also 2 machine hour in polishing department
So I multiply the 6 machine hour by 1.58
I make the same assumption for labour hours and multiply the 8 by 1.87$

But book calculate like this
Overhead to be absorbed
Assembly $1.58 x 4 hours
Polishing $1.87 × 5 hours

What’s the logic behind this calculation

Thank you for your attention and I am sorry If it becomes too long