According to Expected Utility Theory (with a concave utility function u(.)), if one is indifferent between a sure wealth level w-y and a bet of (w-x,p;w,1-p), please derive that one should prefer the bet (w-x,(1-r)p;w-y,rp;w-ry,1-p) to the sure wealth level w-y, where 0x>y>0