consider an economy in which the marginal product of labour mpn is mpn= 309 -2n,where n is the amount of labour used.the amount of labour supplied,ns is given by ns = 22+12w+2t. where w is the real wage rate and t is the lump-sum tax levied on individuals. use the concepts of income effects and substitution effects to explain why an increase in lump-sum tax will increase the amount of labour supplied.