is a 2 point sente (1 pt. under territory scoring). 
gains 2 points, because White is komonster, as explained earlier. 
gains 1.75 points and then 
gains 1.5 points. Then the players share the dame and protective play. 
could be a pass, but it costs nothing and allows us to count territory. White has 10 points of territory and Black has 11, to win by 1 point. (The original position is worth 0.75 for White; Black gained 1.75 in the play.)The next diagram shows correct play by territory scoring.
White wins the ko.
is a 1 point sente. gains 0.75 point. gains 0.5 point, because White is komonster. Each player has 12 points, for jigo. (The original position is worth 0.25 for White. Black gained 0.25 in the play.) would be a mistake under area scoring. The next diagram shows best play after that.
takes ko.
fills the ko.
costs nothing. Result: White wins by 1. is a 2 point sente. gains 1.75 point. 
gains 2 points. The original position is worth 0.75 for White. Black lost 0.25 in the play.
and 
are a miai pair of dame, which act as a tertiary ko threat. A tertiary threat is a defense against komonster. If filled the ko, Black would get a dame in the ko exchange. In this position it did not matter because White had another ko threat, but
was a sente to eliminate Black's tertiary threat at 5.Kim Yonghoan also discovered komonster and tertiary threats. When we were getting to know each other around 20 years ago, we had a strange exchange of emails. Each of us thought that we knew something the other didn't, and we were a bit coy about our "secret".
Why "tertiary" threats? When I was learning go, the beginner literature said that a ko threat was something played to win the ko. OC, the opponent might not answer it. As I began to study ko, I realized that you might play a ko threat in order to make a gain if it were not answered. So a primary threat is one played to win the ko and a secondary threat is one made to gain something in the ko exchange. A tertiary threat is played to prevent a loss to the komonster.
Edit: Kirby's answer.
OK. Now that we know that White is komonster, we can say that
gains 2 points by area scoring. 
gains 2 points in reverse sente. gains 1.75 points. Then the dame and protective play are shared equally. In the play Black gains 1.75 points to win by 1. In the sequence I gave Black got the last 2 point play, but White got the 1.75 point play. All same same.
fills ko. 
takes dame.
takes dame.
But I did work out a general way to evaluate prototypical ko ensembles. I have not run across anything like this way of evaluating kos in the go literature, despite its practical value, as evidenced by my little problem. I started writing a book about it in 1989, but that was before finding out about combinatorial game theory and Professor Berlekamp's work on kos. 
takes the gote, 
wins the ko; each player gets two points.
.