Answer:
a. $21 per machine hours
b. $4,855 Â Â Â Â Â
Explanation:
a. The computation of the plantwide predetermined overhead rate is shown below:
Plantwide predetermined overhead rate is
= Variable overhead cost rate per machine hour + Fixed overhead cost rate per machine hour
= $2 + (fixed manufacturing overhead cost ÷ Estimated machine hours)
= $2 + ($4,275,000 ÷  225,000 machine hours)
= $2 + $19
= $21 per machine hour
b. Now the total manufacturing cost assigned is
Particulars                    Amount
Direct material                $1,702    Â
Direct labor                 $1,221
Variable manufacturing overhead $168
(84 × $2)
Total variable cost             $3,091
Add:
Fixed manufacturing overhead
(84 × $21)                 $1,764
Total manufacturing cost assigned
to Job P90 Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â $4,855 Â Â Â Â Â