In the first part of your answer you said that there would be a 0.5 probability of winning if our capital is at 50. That is not true, we actually have a 0.4 probability of winning, because the given problem defines the probability of the coin coming up heads as ph = 0.4. You can also see it in the Graph above.
It's only a minor detail, but I still wanted to point it out in case somebody is confused by it.
In the first part of your answer you said that there would be a 0.5 probability of winning if our capital is at 50. That is not true, we actually have a 0.4 probability of winning, because the given problem defines the probability of the coin coming up heads as ph = 0.4. You can also see it in the Graph above. It's only a minor detail, but I still wanted to point it out in case somebody is confused by it.