Determine which of the following functions are one-to-one. a. g1:{1,2,3,4,5}{a,b,c,d,e};g1(1)=b,g1(2)=b,g1(3)=b,g1(4)=a,g1(5)=d b. g2:{1,2,3,4,5}{a,b,c,d,e};g2(1)=d,g2(2)=b,g2(3)=e,g2(4)=a,g2(5)=c c. g3:NN;g3(n)={2n+12nifnisoddifniseven d. g4:NN;g4(n)={n+1n1ifnisoddifniseven