Answer: 2.75 blankets.
Step-by-step explanation:
The opportunity cost is the value of a good that is sacrificed by choosing some other alternative. So, there are certain costs associated with the consumption of some goods.
In our case,
Opportunity cost of producing 1 shirt =

= 2.75 blankets
Opportunity cost of producing 1 shirt is 2.75 blankets which means that 2.75 blankets have to be foregone to produce 1 shirt.