Thank you for the opportunity to help you with your question!
The best graph for kinetic energy is B since it is energy in motion it has to start from zero
The best graph for potential energy is A since potential energy is usually stored energy awaiting motion the garph has to start a point higher and speed of the object will reduce with time the graph will start curving horizontally with time
mass =625kg= 625000 g
ke =1/2* 625000*18*18
when speed =36m/s
Am not seeing the image in q 26 please
Please let me know if you need any clarification. I'm always happy to answer your questions.