T-shirts at a flea market cost $4.50 each and shorts cost $6 each. You have $108. Write an equation in standard form that models the possible combinations of t-shirts (t) and shorts (s) you can buy.

Which of the following is the major negative aspect of crossover designs for research studies? a. prohibitive cost b. residual effects c-subject drepout d. incomplete randomization e. large sample size required