As there is an assumption/release of debt, Mr D is deemed to have acquired a major interest in the dwelling costing £50,000 (so he owns a 20% interest in the dwelling).
Gan fod tybiaeth/rhyddhau dyled, tybir bod Mr D wedi caffael prif fuddiant yn yr annedd sy'n costio £50,000 (felly mae'n berchen ar 20% o fuddiant yn yr annedd).