i dont understand how he got this answer. what is the formula?

om - $2700 + DL - $741 10/30a 13) 13) Calico Corporation produced 2300 units in Job 903. The following data is provided for Job 903 for the year: Direct materials used $2700 Direct labor costs $741 + molt_$18.30.39=$713.7 Actual manufacturing overhead rate per direct labor hour $17.15 Predetermined manufacturing overhead rate $4154.7 per direct labor hour $18.30 4154.7 Direct labor hours used in Job 903 Direct labor rate per hour $19 unit: 2300 - $1.81 D) $18.30 What is the unit cost for Job 903? (Round to two decimal places.) A) 31.81 B) $11.46 C) $1.50