personal pension contribution

hi sir i hope you are doing good, in computing for charges arising on personal pension contribution, which of the tax band will we use to determine the marginal rate of the individual? say for example the employee has total income of 170,000 and gross contribution of 90,000 in the year. this would effectively increase the bands to 127500 and 240000. so the charge can be taxed at 40% or 45% based on normal band? i just did not understood the marginal rate. this is following question 20 of the practice question at the back of the lecture notes. thanks