Sung Mi and So Young bought their house 3 years ago for $500,000 with a down payment of $75,000 and a mortgage of $425,000. Since then, they have paid down an additional $25,000 of the principle and the market value of their house has increased to $650,000. What is the amount of 'equity' they have in their home? O $250,000 O $650,000 O $400,000 $150,000