13 in s. let a be ansycle, b be an s cycl& and y be an t cycle then cabyis even rtstt 0aci (a)ebis venrts even o ac (b) a bis even r+s+2 even (d) aßy is even r+

13 In S. let a be ansycle, B be an s cycl& and y be an t cycle then CaByis even rtstt 0aci (a)eBis venrts even O ac (b) a Bis even r+s+2 even (d) aßy is even r+s+t odd