this problem shows one tricky endgame principe.
Please keep in mind that you are fighting only for one point ko.
(;AW[oc]AW[od]AW[oe]AW[ne]AW[me]AB[nc]AB[nb]AB[ob]AB[pb]AB[pc]AB[pd]AB[pe]AB[qf]AB[re]AW[pf]AW[pg]AB[of]AW[qg]AW[rg]AW[ke]AW[kc]AB[ld]AB[lc]AW[rk]AW[pk]AW[nk]AW[lk]AW[jk]AW[hj]AW[hh]AW[hf]AW[hd]AW[hb]AB[le]AW[lf]AB[gb]AB[gc]AB[gd]AB[ge]AW[he]AW[hg]AW[hi]AW[ik]AW[kk]AW[mk]AW[ok]AW[qk]AB[rl]AB[ql]AB[pl]AB[ol]AB[nl]AB[ml]AB[ll]AB[il]AB[jl]AB[kl]AB[hl]AB[gk]AB[gj]AB[gf]AB[gg]AB[gi]AB[gh]AW[hk]AB[gl]AW[hc]AW[ha]AB[sk]AW[sj]AB[sl]AW[rj]AB[ga]AB[rf]AB[sf]AW[sg]AB[rc]C[Black is fighting for one point ko. How many ko threats can he get here?]AB[mf]AW[kd]AB[kb]AB[mb]AB[la]AW[jb]AW[ja]AB[md]AW[ka]AB[lb]AW[nf]LB[jj:2]LB[kj:3]LB[lj:4]LB[mj:5]LB[nj:6]LB[oj:7]LB[pj:8]AP[goproblems]
(;B[jj];W[ij]C[Ok, showtime!]
(;B[ng];W[mg];B[nd];W[mf]C[Yes!RIGHT])
(;B[nd]
(;W[mg];B[ng];W[mf]C[RIGHT]))
(;B[kf];W[mg]C[This exchange was one free point for white as he would have to play N13 anyway and black put one stone into his territory.]))
(;B[kj];W[jj]C[Where?];B[kf];W[mg]C[Black move was bad as white just gained one point now. Not useful when fighting for one point ko.])
(;B[lj];W[kj]C[Play them!];B[kf];W[mg]C[White just gained one point now!])
(;B[mj];W[lj];B[kf];W[mg];B[lg];W[mf];B[jc];W[jd];B[id];W[ic];B[je];W[jc]C[Five ko threats, but white gained one point here. White played N13, which was in fact neutral point, while black gived white one prisoner by cutting at L14.])
(;B[nj];W[mj]C[Ok?];B[mg];W[ng];B[kf];W[lg];B[kg];W[mh];B[jc];W[jd];B[id];W[ic];B[je];W[jc]C[Six ko threats, but white gained one point there - not very useful when fighting for one point ko.])
(;B[oj];W[nj]C[Showme];B[kf];W[mg]C[Too bad. L14 was one bonus point for white as N13 played by white was a neutral point!])
(;B[pj];W[oj]C[I dont see so many threats there.]))