Question $4$

A stock price is currently $$30.$ During each two$-$month period for the next four months, it is expected to increase by $8\%$ or reduce by $10\%.$ The riskfree interest rate is $5\%.$ Use a two$-$step tree to calculate the value of a derivative that pays off $[max(30-S_T,0){]}^2$ where $S_T$ is the stock price in four months?