Please answer this right! I always get these wrong

Required information [The following information applies to the questions displayed bolow.] Warnerwoods Compary uses a perpetual inventory system. It entered into the following purchases and sales transactions for March. 4. Compute gross profit earned by the company for each of the four costing methods. For specific identification, units sold include 125 units from beginning inventory, 255 units from the March 5 purchase, 105 units from the March 18 purchase, and 145 units from the March 25 purchase. Note: Round weighted average cost per unit to two decimals and final answers to nearest whole dollar