Two elements X and Y have atomic weights of 14 and 16 respectively. They form a series of compounds A, B, C, D and E in which the same amount of the elements X and Y are present in the ratio of 1:2:3:4:5. If the compound A has 28 parts by weight of X and 16 parts by weight of Y, then the compound C will have 28 parts by weight of X and: