Aconstruction worker is making concrete by mixing sand, gravel, and cement in water. for each pound of sand, he uses 1 2/3 pounds of gravel. for each pound of gravel, he uses 2/5 pound of cement. he is making enough concrete that he needs to use 3 pounds of sand. how many pounds of cement does he use? a. 1 pound b. 1 4/15 pounds c. 2 pounds d. 2 1/15 pounds