please explain

the calculations

Calculate the amount of disodium EDTA (powder) needed to prepare 4mM disodium EDTA in a 20mL solution. ( MW of disodium EDTA =372.24g/mol) Calculate the amount of MgCl2 (powder) needed to prepare 5mMMgCl in a 20mL solution. (MW of MgCl2=203.3g/mol) Calculate the amount Triton X-100 (liquid) needed to prepare 0.75% Triton X100 in a 20 mL solution. Calculate the amount of 1M Tris- HCl needed to prepare 20mM Tris- HCl in a 20mL solution