Which explanation correctly solves this problem?

chris was putting a railing on his deck. at the end of the day, he had 11.5 feet of railing left over. during the day, he had used two 1.5-foot-long piece of railing, one 3.25-foot-long piece of railing, and one 6-foot-long piece of railing.

how many feet of railing did chris have at the beginning of the day?

a.
start with 11.5. multiply 11.5 by 2. add 1.5 and 3.25 and 6.

b.
start with 11.5. multiply 1.5 by 2. add this product to 11.5. then add 3.25 and 6 to the answer.

c.
start with 11.5. add 1.5 and 3.25 and 6. multiply the answer by 2.