Which explanation correctly solves this problem?

karl was fixing the molding around his pool. at the end of the day, he had 10.5 feet of molding left over. during the day, he had used one 3.5-foot-long piece of molding, three 2.25-foot-long piece of molding, and one 5-foot-long piece of molding.

how many feet of molding did karl have at the beginning of the day?

a.
start with 10.5. add 3.5 and 10.5. multiply 2.25 by 3 and add the sum and product together. then add 5 to the answer.

b.
start with 10.5. add 3.5 and 10.5. add 2.25 to the sum. then add 5 to the answer.

c.
start with 10.5. add 3.5 and 2.25. add this sum to 10.5.