Solving a differential Calculus problem with Python

Problem Statement

A mixing tank with a volume of 10 liters contains a salt solution at a concentration of 120 g/L. If salt-free water is continuously fed into this tank at the rate of 15 L/h, and the volume is maintained constant by continuously overﬂowing the excess ﬂuid, what will be the concentration of salt after 90 min.

Solution

def salt_in_g(volume, concentration):
    grams = volume * concentration
    return grams

def in_flow(water_in_l, delta_t):
    volume_add = water_in_l_h * delta_t
    return volume_add

volume = 10
concentration = 120
total_grams = salt_in_g(10, 120)

water_in_l_h = 15
delta_t = 1 / 216000

for _ in range(1, 90*60*60):
  gram_out = salt_in_g(in_flow(water_in_l_h, delta_t), concentration)
  total_grams = total_grams - gram_out
  concentration = total_grams / volume

print(concentration)