two sentences are good, but I think the second sentence is more suitable

The first parts are both possible. I have been pleased by your efforts. This is present perfect, as you probably know, and so it includes the present. It implies that I am pleased now with your efforts and I was pleased before now (so past + present). So I have been pleased, describes the past and present. I was pleased by your efforts. This is the past tense. There is no information about the present. All we know is that the speaker was pleased in the past. So now the second part. I can be pleased now for a past solution. So the first sentence is possible. The second sentence seems strange. The PM was pleased in the past for a solution that includes (in some way) the present [as well as the past]). I think stylistically we would prefer sentences like this: The PM is pleased that it has been solved. The PM has been pleased that it was solved. The PM was pleased that it was/had been solved. Personally, my first option would be my choice for present time.

Why? An English teacher said the first is more suitable. He said:"the first parts are both possible. I have been pleased by your efforts. This is present perfect, as you probably know, and so it includes the present. It implies that I am pleased now with your efforts and I was pleased before now (so past + present). So I have been pleased, describes the past and present. I was pleased by your efforts. This is the past tense. There is no information about the present. All we know is that the speaker was pleased in the past. So now the second part. I can be pleased now for a past solution. So the first sentence is possible. The second sentence seems strange. The PM was pleased in the past for a solution that includes (in some way) the present [as well as the past]). I think stylistically we would prefer sentences like this: The PM is pleased that it has been solved. The PM has been pleased that it was solved. The PM was pleased that it was/had been solved. Personally, my first option would be my choice for present time."

The second is more suitable

The prime minister WAS pleased that the traffic problem WAS solved. The prime minister IS pleased that the traffic problem HAS BEEN solved. Your sentences need to remain in the same tense. Using 'has been' after 'prime minister' sounds like he was happy about it, but the speaker doesn't think that it will stay that way. As 'has been' is present perfect tense, it indicates that the action (the prime minister being happy) began at some time in the past, is still in progress and might not stay as such.