Answer:
$56 
Step-by-step explanation:
Given: 
Maria paid for ticket = $12 
If she worked = $44 (earn) 
Opportunity cost = ? 
Computation of opportunity cost: 
Opportunity cost = Maria paid for ticket + Sacrifice earning 
Opportunity cost = $12 + $44 
Opportunity cost = $56 
Opportunity cost is a type of Imaginary cost that denote, what an individual or firm has to give to gets other opportunity.