Let marked price of lunch buffet = Rs. 100 When discount of 20% is given, => Selling price of ticket = $$frac{(100 - 20)}{100} imes 100 = Rs. 80$$ Let cost price = $$Rs. x$$ => Profit % = $$frac{80 - x}{x} imes 100 = 42$$ => $$frac{80 - x}{x} = frac{42}{100} = frac{21}{50}$$ => $$4000 - 50x = 21x$$ => $$21x + 50x = 71x = 4000$$ => $$x = frac{4000}{71} = $$ Rs. $$56.33$$ If discount is 15%, => Selling price = $$frac{(100 - 15)}{100} imes 100 = Rs. 85$$ => Profit % = $$frac{85 - 56.33}{56.33} imes 100$$ = $$frac{2867}{56.33} approx 50.875\%$$ => Ans - (B)