$24)$If goods are complements, for sure their a$.$ Cross price elasticities are positive. b$.$ Cross price elasticities are negative. c$.$ Cross price elasticities are zero. d$.$ Income elasticity is negative e$.$ Income elasticity is positive. $25)$Demand is perfectly inelastic when a$.$ The good in questions has perfect substitutes b$.$ Shifts in the supple curve results in no change in price. c$.$ Shifts in the supply curve results in no change in quantity demanded. d$.$ Shifts in the supply curve results in no change in the total revenues e$.$ An upward shift in the supply curve results in a decrease in the total revenues $26)$The income elasticity of demand is high for $6$ a$)$ shelter b$)$ luxuries c$)$ clothing d$)$ food e$)$ inferior goods