Answer:
a) 計 -> 古 -> 吐 -> 堀
計 KEI, haka(ru), haka(rau) - plan, total, measure
古 KO, furu(i) - old
吐 TOU, ha(ku) - spew, vomit, give vent to
堀 hori - moat, canal, ditch
b) 切 -> 召 -> 員 -> 贈
切 SETSU, ki(ru), ki(reru) - cut
召 SHOU, me(su) - summon, wear, take
員 IN - member
贈 ZOU, SOU, oku(ru) - give, present, bestow