Find the slope and y-intercept

Li buys supplies so he can make and sell key chains. he begins to make a profit only after he sells 4 key chains. what point on the graph makes the most sense in this situation?

Can someone check if i did this right since i really want to make sure it’s correct. if you do you so much

Which graph has figures that can undergo a similarity transformation to justify that they are similar? (obviously not the third one)