Question 30A house worth $\$9000$ is sold by Mr. $A$ to Mr. $B$ at a $10\%$ loss. Mr. $B$ sells the house back to Mr. $A$ at a $10\%$ gain. The result of the two transactions is:Mr. $A$ breaks evenMr. $B$ gains $\$900$Mr. $A$ loses $\$900$Mr. $A$ loses $\$810$Mr. $B$ gains $\$1710$