Answer:
See Explanation
Explanation:
Given

Required
Which represents 400km
This question requires options. Since none were given, I will answer on a general term.
Situation 1:
s = 20km/h and t = 20h



Situation 2:
s = 10km/h and t = 40h



Situation 3:
s = 40km/h and t = 10h



So, all you literally have to do is multiply the values of s and t. If the product gives 400, then; that situation is D = 400