• (a) / (a) (b) 6 (b) (a) (b) (c) H2(g) (a) 48 E2 (a) (i) (a) I (ii) (b) / (iii) (b) (b) (c) / 2760 1766 +852 B1(a) / (d) +852 2978 6870 +852 2760 1767 351