Please I need today answer for This question and it is very important and I need solution for this i

Please I need today answer for This question and it is very important and I need solution for this issue with all the details , and help me with all the details.Please write your answer to me by typing, not by handwriting, so that I can read and understand your answer clearly.BR/Hassan

a) What is the difference between a utilitarian social welfare function and a Rawlsian social welfare function?

b) Define the marginal rate of substitution.