task assignment algorithm

good day

i'm building a system that user will withdraw money and deposit money. this is how it should work: lets take i have 3 users who want to deposit money(user1=$200, user2=$400,user3=800) and i also have 5 users that want to withdraw money(user1=$200,user2=$300,user3=$100,user4=$450 user5=$350).

can you please help me on how i should implement this.

thank you

mankhensa

south africa