Calculate the CGT payable in relation to each of the following disposals, assuming in each case that the annual exemption is fully utilised against other gains, that there are no allowable losses and that ER is claimed wherever possible. The taxpayers concerned have made no previous ER claims.

(a) On 31 May 2017, Roger sold all of his shares in a trading company, realising a gain of £351,000. He has owned 25% of the company's ordinary share capital since March 2012 and has been a director of the company since June 2013.

(b) On 31 July 2017, Dennis sold his business (which he has owned since May 1990) and realised gains of £15,250,000 in relation to relevant business assets.

(c) On 31 August 2017, Denise sold her interest in a trading partnership and realised gains of £140,000 in relation to relevant business assets. She had been a member of the partnership for five years. Also on 31 August 2017, she sold a building which was owned by her personally but had been used by the partnership for business purposes since 2014. She realised a gain of £31,000 in relation to this building.