How to get the desired output by adding N number multiplied by M times and so on in Python

Question

Is there's a library to get the desired output with n number m times for example

selection_from = {'a':30.2,'b':21,'c':2.1, 'd':73.2}
desired_output = 98372

#get input >> user can select from selection_form
user_selection = ['a', 'c']
# get something which satisfy this equation 
# m * selection_form['a']  + n * selection_form ['c'] <= desired_output 

Result should be close to desired output

Answer 1

simple straight forward answer would be

selection_from = {'a':30.2,'b':21,'c':2.1, 'd':73.2}
desired_output = 98372
user_selection = ['a', 'c']
summ=0
for x in user_selection:
    summ+=  selection_from[x]  
m=n=desired_output/summ

output:

(m,n)=(3045.572755417957, 3045.572755417957)

!this is possible solution if m and n can be rational if at all they need to be integers this wont be perfect fit as a solution