To graph the equation between 0 and 5 start with the ordered point (0,100)

You know that in 1 hour the amount will be times the amount at 0 so you get the second ordered pair of (1,400)

Plot the others similarly and draw the graph

Spoiler:

As the graph is exponential growth I suggest using a log scale on the y axis

which gives a straight line in the form

Edit: Plot against to get the straight line, with gradient and y intercept